The Basics of Aether Raids Defense

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In Aether Raids, there are 2 halves to the game mode. In this guide, we will focus on the defense portion of Aether Raids; namely some of the basics of crafting an Aether Raids Defense, and some of the more advanced tricks that could be used.

The maximum penalty of an Aether Raid Defense match is -80. The goal of Aether Raids Defense is to reduce your lift loss when people are attacking you. This could be done in 2 ways.

  1. Defeating the attacker’s units. For every unit you defeat, you drop your penalty by 20. If you win the battle, the penalty is negated.
  2. Fielding defensive Mythics and blessed units. Penalty reduction is calculated by the product of the number of matching defensive Mythics you field (maximum of 2),the number of matching blessed unit (or matching Legendary Heroes), and 5. You can see the maximum lift loss when fielding your defense team.

Regarding the second point, while fielding Legendary Heroes can be counted as a matching Mythic Blessed hero in the corresponding season, it also meant that players will have to fine-tune their defense map every week if they care about the performance of the map. The abundance of defensive blessings every 2 weeks meant that it might be more worthwhile to bless some units specifically for defense to reduce the need of maintenance.

Furthermore, Mythic Blessings also provides bonus stats that are dependent on the Mythic Hero that is on the defence team. This not only applies for defensive blessings of Anima and Dark, but also Light and Astra. While Light and Astra do provide the stat bonuses, they do not result in reduction of lift loss as mentioned above.

In this guide, we will specifically focus on some core concepts of creating a defence team in terms of countering against common strategies. It is highly recommended for players to read the offence guide before proceeding with this guide.

Basic Guide to Game AI

As defence map is largely influenced by how the game (AI) controls your units. For ease of reference, a copy of the AI guide in the Introduction guide is pasted below.

Your map units will be controlled by the game, and as you learn from general gameplay, it is easily exploitable. As such, understanding how the AI controls your units is paramount to your map’s success. The AI of Fire Emblem Heroes is mostly a well-documented topic, however things can get complex relatively quickly, so this section is a brief summary of how the AI works.

There are 2 queues when managing attacks; the support queue and the attacking queue. If there are no valid targets and the AI is activated (either the attacker puts a unit in range, or initiated on the defense), units will be in movement mode instead.


  1. If a unit deals 5 or more damage to the opponent, the unit will be placed in the attacking queue
  2. Wins > Draws > Losses. AI will select the best possible outcome possible.
  3. Afflicting statuses and debuffs on target will have a higher priority if it matches the best possible outcome in point 2.
  4. The attacker is then selected by the damage it deals and takes. Obviously the higher the damage dealt, and the lower the damage taken the better. AI will select the best result.
  5. Slot order can be used as a final tie-break, however it is rarely utilized as ties in outcome occurs rather rarely.


  1. All units that are out of range with valid assists will be placed in this queue. Validity is dependent on the assist types.
  2. Rally: Unit will rally any ally that is in range of attacking the opponent if the ally receives at least 2 points in 1 stat. 
  3. Rally Up: Unit will rally a target that will buffs the most number of valid ally. Validity is the same as normal rally.
  4. Dance / Sing: Unit will dance if there is a unit near the dancer that already used up its turn.
  5. Heals: Unit will heal if any of the ally is missing sufficient HP. For Restore users, they also heals if any ally has a status ailment. Heals are prioritized over attacks unless the attacks kill.
  6. Positionals: Unit will use on a target ally if it reduces the number of enemies that could reach the target.
  7. For the final position of the assists, teleports (such as using Guidance and Aerobatics) and defense tiles have higher priority.
  8. Slot order can be used as a final tie-break if applicable.


  1. For movement priorities, no assists before assists, melees before ranged before no weapon.
  2. Distance from opponent units can be used as the first tie-break, however it is very difficult to control on defense.
  3. Slot order can be used as a final tie-break if applicable. This is more commonly used here compared to the other 2 sections.

Countering Enemy Phase

A good understanding of the offensive strategies available is imperative in preparing for a good defense. For a first step, if you had not done so already, read the offensive guide for more information.

There are predominantly 2 strategies that are Enemy Phase focused; Vantage and Pure Enemy Phase. In this section, we will cover some of the counters against these enemy phase strategies.


An overload (or overlap) in the context of a defense is to have multiple units that could hit any spot at any different time regardless of approach. The objective of having an overload is to ensure that there is always an advantageous match-up for your defense. This includes Weapon Triangle advantages, effective damage weaponries, or simply sheer stats.

In general, there are 3 types of overload; Natural, Rally-based and Movement-based. 

Natural Overload

Example of Natural Overload (Flierball)

Natural overload is probably the easiest to understand; the natural attack range of all your units naturally overlaps. This meant that there would always be multiple units attacking any given spot. The above could be achieved by simple positioning, or movement skills such as Aerobatics, Guidance and Ground Orders

The simplicity of such a strategy is both a boon and a bane. Natural overloads are the easiest to assemble as you do not need much understanding of the AI to figure it out, but naturally the opponent would also be very aware of it as well. If the Overload involves ranged units, a well-placed Tactics Room or debuffers such as Loki could also potentially foil your plans.

Another potential issue is the safety of your units when achieving a natural overload. As most maps in Aether Raids are also relatively open, there are also not much room in creating a natural overload which does not inhibit the safety of your units. 

Rally-based Overload (Rally Trap)

Example of Rally-based Overload

A Rally-based overload is as stated on the header; utilizing a rally to create overloads. This is also commonly known as a “Rally Trap”.

The set-up usually involves a unit that is usually is not in range of attacking with a rally equipped. If the attacker directly baits a unit directly in range, the rally ally would then rally a unit in range due to how the AI works. 

Here are the main clauses that affects a rally set-up (extracted from the AI guide):

  • Rally: Unit will rally any ally that is in range of attacking the opponent if the ally receives at least 2 points in 1 stat. 

  • Rally Up: Unit will rally a target that will buff the most number of valid ally. Validity is the same as normal rally.

  • Slot order can be used as a final tie break if applicable.

A simple Rally Trap would most of the time be accompanied by a dancer to allow the said rally unit to attack, with the most common dancer being Legendary Azura due to Gray Waves granting extra movement. This allows the defender to create a larger overload. A more sophisticated one would combine it with movement skills to allow even more overlaps to occur.

Movement-based Overload

Example of Movement-based Overload

Movement-based overloads are additional overlaps that do not happen immediately. They only happen when all units are no longer in range and are in movement mode. A movement-based overload exploits how movement is prioritized. Below is the relevant excerpt from the AI guide:

  • If there are no valid targets and the AI is activated (either the attacker puts a unit in range, or initiated on the defense), units will be in movement mode instead.

  • For movement priorities, no assists before assists, melees before ranged before no weapon.

By positioning the said unit with no assist nearby and having a dancer just behind, this could also indirectly create an overload. One issue of this type of Overload is that the AI could go in the wrong direction, which may not lead to the correct overlap. A possible solution is to use structures to guide them in the right direction.

Countering Vantage

For most units, Vantage is mainly accessed from a B-slot Passive. If a player wishes to counter Vantage strategies, preventing counter-attacks or skills that influence attack priority (also mainly known as “Hardy Bearing” with reference to the seal) are the main ways of dealing with Vantage. Here are some ways that counters against Vantage strategies that is not weapon specific.

Hard Counters

  • Firesweep weapons and Dazzling Staff users prevents counters for all units altogether, as most units could not run Null C Disrupt and Vantage at the same time.

  • Windsweep and Watersweep takes up the B slot of your units and stop them from following up, however their counter prevention by a speed check could be used as a Vantage check due to the same reason as Firesweep. They are however more weapon specific.

  • Hardy Bearing seal itself is the most intuitive check against Vantage. Weapon with similar effect (such as the daggers from Hoshidan Summer) also works as counters.

Soft Counters

  • Panic weapons. Usually Vantage units are reliant on visible buffs due to difficulty in their support being in range. This meant Panic weapons are particularly effective to reduce the amount of potential damage dealt.

  • Dull Ranged and the Lull skills (specifically the ones that reduce ATK) are also useful due to the same reasons.

Instant Specials

In many Legendary and Mythic Hero Battles, the foes in battle usually have some form of special that is instantly charged. The potency of such a strategy could be replicated in an Aether Raids Defense by overwhelming an enemy tank with instant specials. Coupling it with vantage counter skills ensures that the kill is more likely to occur.

Using a combination of special charging abilities, which includes skills such as Ostia’s Pulse, Quickened Pulse and Infantry Pulse, it is possible to charge specials that previously not possible in their first hit. This could be further combined with weapons such as Ouch Pouch and Dark Excalibur to charge specials of higher cool down. Most of the time, there is a positive correlation between the strength of the special and the cool down, so charging high cool down specials increases your team’s firepower in the player phase.


Attackers love their buffs, so having a unit that could potentially reverse the buffs of the attacker limits their options. Even if the attacker chooses to not use any visible buffs, it can be considered a small victory as your defensive units will face unbuffed opponents rather than buffed ones. This could then be combined with overloads to ensure that survival in the enemy phase is difficult to achieve.

Unfortunately, the convention means of landing Panic, such as Panic Ploy, is difficult to perform on very stacked Enemy Phase units. On-hit Panic is likely a more reliable approach to do so. The most accessible skills that could do so are Panic+ and Legion Axe+. Panic Smoke could also be used if it is available for the player, however it could be problematic as it requires the survival of the smoke wielder, which is not guaranteed.

Countering Player Phase

The 2 main strategies to consider when defending in the player phase are Galeforce and Hit-and-Run. Galeforce is predominantly based around melee units, while Hit-and-Run units are mainly ranged. This meant that a good team needs to balance between able to defend against melee and ranged threats.

Trap Placements

Trap Placements should be predominantly used to protect your units. If the defense units could not reach the traps, there is no pressure for the opponent to test the traps and run away. This meant that the trap is potentially wasted, as it could be better utilised to shut down the player phase strategies.

If a particular unit is at risk of being an entry point of Galeforce, or is just weak to melee units, putting traps at those spots could be ideal. Whereas, traps could be placed 1 space away if a particular unit is weak to getting attacked from ranged.

The most ideal placement for a trap is where the attacker finds it difficult to get out of range if the trap is real. The most common way of testing traps is using Smite, which pushes the unit forward by 2 spaces. As long as the opponent could not Smite onto the trap, the opponent would be less likely to go for the traps unless for desperate measures.

However, placing traps that is difficult to test depends on the threat range of all your units, in particular the frontline. Assembling the frontline is something that needs to be examined in further detail.

Building a frontline

Building a frontline is important to defend against both player phase strategies to protect your less durable members. A frontline unit could either be part of your offensive strategy during the attacker’s Enemy Phase, or could simply be focused on protecting the units at the back.

As mentioned above, the threat range of your frontline is something that you should consider. The threat range is essentially the maximum reach of the units with the frontline included, which determines the amount of space you give to your opponent.

Frontline units that could attack from 4 spaces away (Ranged 3-movement) have the longest reach, which gives the opponent little space to prepare an attack. However, it is easily locked down by Tactics Room or Loki, as most do not have enough HP to avoid the debuff. There are defensive strategies, such as a full line of ranged cavaliers that solely focus on giving the opponent as little space as possible.

Cavalry Line
  • Frontline units that could only attack from 1 space away (Melee 1-movement) would be unable to have a lot of protection using traps, as all traps would be possible to test using Smite. For teams using such a frontline, traps are not exactly a good way of protecting your units, and players should seek other means of doing so. This will be covered later.
  • The most common frontline units for consideration would be those that could attack from 2 spaces away (Melee 2-movement or Ranged 1-movement). The traps that are adjacent to the frontline unit are very difficult to test using smite, while the traps 1 space away are not. This meant that such frontline could be vulnerable to an attack from range, so it is ideal for the player to have some form of mechanics within the frontline unit to protect itself. This includes Brave Ike’s Urvan and Seliph’s refined Tyrfing.
  • Frontlines that attack 3 spaces away (Melee 3-movement or Ranged 2-movement) could guard both adjacent and 1-space away traps. This meant that testing traps is very risky for the opponent. However, as there are only 4 traps (fake traps inclusive), it is up to you to decide what to prioritize, and where are the common approaches from your set up.
  • Frontlines that attack 4 spaces away (Ranged 3-movement) are focused on reducing the amount of space for the attacker to work with. However, most units that are ranged and has 3 movements tends to be rather frail by default. These type of frontline probably needs more support from the other teammates. This is covered in the next section.

Buffs and Formation

Stacking buffs is not something that only the attacker could do. Buffs could be used to either bolster your offenses further, or make your units harder to take out in general. However it is difficult to suggest visible buffs as a basis of supporting your team, as not only is it not stackable, it is also susceptible to Panic from the attacker. As such, we will mainly focus only on combat buffs.

  • Buffing ATK potentially protects a unit from Galeforce, as it increases the threshold required to pass checks using Heavy Blade or similar skills. It can also be used aggressively, albeit more difficult to do so if the opponent initiates on the defense.

  • Buffing SPD is similar by increasing thresholds for Flashing Blade or similar skill. It could also be used to prevent attackers from outspeeding your units, which is relevant for both melee and ranged foes.

  • Buffing DEF / RES increases the threshold required to take the unit out.

Combat buffs usually has a range of 1 or 2 spaces. By using combat buffs that has 2 range, stacking combat buffs is a valid strategy to protect your units. The closer the units are, the more you could stack the combat buffs. However, it could also backfire as stacking combat buffs usually requires the defense team to be closely packed together, which means vulnerability to skills such as Sabotages and Yune Whispers.

If your team is fully made up of units of fliers, cavalry, armor, dragons or beasts, it is also possible to use Wards and Goads of its corresponding type. These combat buffs are much more potent and versatile due to its stricter team requirements. Specifically to counter aggression from attackers, using multiple wards provides the whole team a large boost in defenses, making them hard to take down. 

Galeforce Prevention

Galeforce teams usually rely on special acceleration from Flashing Blade or Heavy Blade to activate, and also rely on being able to take a unit out with Galeforce to ensure the Galeforce unit’s safety. This meant there are 2 possible counterplays against Galeforce other than using traps.

  • Making your frontline harder to take out.

  • Slowing your attacker’s special charge.

The former could be done by simply bulking up your frontline with other skills, and use potentially wards to bolster it further. The latter could be done by using skills such as Guard and Hack’o Lantern+. If a player is short of traps to protect his units from Galeforce, he should consider these factors to mitigate this weakness.


Sometimes, a player might look to activate your team’s AI by attacking your units and running away using a dancer and a positional assist skill. One counter-play is to have a unit to potentially chase the unit that is running away.

The set-up is similar to setting up a movement-based overload; have a unit (ideally ranged) that has no assist and a dancer that could reach the unit that moved. This ensures that at least 1 unit on your team would attack.

Defensive Structures

Unlike offensive structures, there is little to no opportunity cost in fielding the maximum number of defensive structures. However, due to scoring favoring offense heavily, players should only consider upgrading their defensive structures after they complete at least the Escape Ladder (which is the highest priority).

Higher Priority

  • Healing Tower
  • Catapult
  • Panic Manor
  • Bright / Dark Shrine
  • Tactics Room
  • Duo Hindrance

These structures are the main buildings to consider when creating a defense team. While it is up to the player's preference, the order above is our suggestion.  Healing Tower helps to ward against Bolt Tower and Savage Blow stacking, Panic Manor could further disrupt the attackers by inflicting Panic, Bright and Dark Shrines is useful to debuff the main units, and Tactics Room delays the ranged units from reaching your units. Due to the prominence of high-level Bolt Towers, the Catapult is becoming increasingly relevant to shut down at least half of the most common Bolt Tower locations (down the middle).

The prominence of many Duo units in the current state of the game does mean that Duo Hinndrance became a much larger part of the game by stopping the attacker from using the Duo Skills. However, do take note that for the structure to take effect, not only it must remain on the field, you must also have a surviving Duo unit in the team as well. This meant that the attackers have 2 ways of deactivating the Duo Hindrance; destroying the structure or destroying the duo unit. 

Lower Priority

  • Schools
  • Bolt Trap
  • Gravity Trap
  • Bolt Tower

Schools can be potentially useful by inflicting debuffs on the foes of the said movement type. There are some situations where a school can be helpful; indirectly stopping Mila from isolation by inflicting debuffs to the dancer's row, or inflict penalties such that the attacker is unable to take down your frontline. However, with debuff reversal effects (such as those of Chaos Ragnell and ATK/RES Unity being available) and debuff negation effects (such as Purifying Breath and Slick Fighter) being more prevalent, it can be difficult to argue for the use of schools in the modern era. Regardless, while schools are now lower in priority, they can still be relevant when the player accounts for the risk. 

The same could not be said with the remaining 3 structures; the payoff for upgrading these structures is not worth the risk and the potential damage it causes to your team. It is recommended for players to avoid upgrading these structures unless they know what they are doing.

Unlike Bolt Tower on Offense, Bolt Tower on Defense most of the time is a terrible proposition, as the players could either avoid it by not walking into the range at Turn 3 or actually use the damage against you to get into either Wings of Mercy or Vantage thresholds.

The role of traps is mainly to protect the potential gaps in your team. As the trap effects can harm your allies as well, most of the time upgrading these traps can be rather problematic. For Gravity Trap, a highly leveled one could potentially inflict the debuff on your frontline. This is especially true if the defense team does not utilize Mythic Blessings. Whereas for Bolt Trap, the same argument of the Bolt Tower could be made against the Bolt Trap. As such, players should avoid upgrading the traps as much as possible.


In this guide, we discussed some of the basic behaviors of the AI, and some considerations that should be considered when creating a defense team. Using the core principles of the above guide would allow you to exert your creativity and understand a defense’s strengths and weaknesses.

Lastly, setting up a defense is not a sprint; its a marathon. Players should always review their defense, and ask for feedback from your peers. Consistently testing and improving is imperative for a good defensive record.

Aether Raids Defense is one of the few places in which players could use their favorite units and seeing the results fully recorded. So do your best and have fun!

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About the Author(s)

Maskilraid is a writer specialising in Fire Emblem Heroes. He situates in the tiny island of Singapore, and is a fanatic in crafting Aether Raids Defence teams. He also has academic background in Statistics, providing statistical analysis of the pull rates in Fire Emblem Heroes.