Bartre

Preferred IV: +ATK or +SPD / -RES or -HP

• At a low amount of investment, Bartre will usually prefer Attack for the largest one-hit damage possible especially on armored enemies.
• With a Speed Asset as well as investment in some skill slots (such as Fury doubly applied in Axe of Virility and the A slot) however, Bartre can reach a respectable amount of defensive Speed while doubling exceptionally slow enemies.
• Bartre's Resistance is outright unsalvageable and should be taken as the Flaw at zero merges. HP isn't a bad one to fall back on if the former is unavailable, and even helps Bartre activate Vantage easier.

Weapon: Axe of Virility (+Eff)

• Axe of Virility's base effect provides effective damage against armored enemies—which already makes Bartre quite valued in high-scoring Arena Assault environments where those foes are copious.
• In addition, when effect refined, Axe of Virility gains an innate Fury effect, making Bartre simply stronger in general. In essence, Bartre can virtually have two good offensive A slot skills at once.

Assist: Reposition / Draw Back / Flexible

• The Assist skill should be tailored towards your personal preferences and team needs, though Reposition and Draw Back are, as always, great recommendations as their single-space pullback rescues allies from enemy territory easily.  

Special: Glimmer / Moonbow / Luna / Bonfire / Draconic Aura

• Bartre's specialized but narrow matchups against armored enemies means shorter-charged Specials—Moonbow and Glimmer in particular—are ideal. Either choice is fine as the former scales off of Axe of Virility's already-insane effect damage on armors, while the latter also scales well off these same targets' usually high Defense stats.
• A Special with a cooldown of 3 is also considerable for their usually higher burst damage; their higher activation rate also means Bartre can potentially save his chosen Special for a higher-priority target. Like Moonbow, Luna is extremely solid against high Defense enemies, while either Bonfire or Draconic Aura tend to offer solid burst off of Bartre's high Defense or Attack respectively. The choice between the latter two depends on your Bartre's finalized stats and which you're able to manipulate consistently.

Passive A: Fury 3 / Death Blow

• For optimal low-investment skills, Bartre doesn't need to look further than his great default Fury 3 (which offers fantastic stat padding all-around and doubly applies with the effect of Axe of Virility) and Death Blow (recommended for slightly superior one-shot damage).  

Passive B: Axebreaker / Vantage

• Axebreaker is both easily available (from any low rarity Laslow) and useful as the majority of armored units are axe-wielders, allowing Bartre to ignore their Fighter skills and likely take them down in one round.
• Because of the self-inflicted damage from Axe of Virility and Fury after each round of combat, Bartre often finds himself at low health. This makes Vantage an option worth pondering as it allows Bartre to unleash a hit on incoming melee enemies before they can attack, making him well suited to battling close-knit armor mobs and weak/weakened enemies in general.    

Passive C: Drive Res / Flexible

• On a budget, Bartre doesn't have to think too hard on his C slot skill as it's mostly inconsequential to his role. For optimization's sake, Drive Res is worth considering as it provides an in-combat Resistance boost for allies that can take magic attacks in Bartre's stead.

Sacred Seal: Sturdy Blow / Chill Def / Atk +3 / Brazen Atk/Def / Brazen Atk/Spd / Flexible

• Straight Attack-boosting Sacred Seals, such as Atk +3 and Sturdy Blow, are generally best for damage improvement and better scaling on armored enemies.
• A Brazen Atk seal of choice takes some setup as they only activate below 80% HP, but considering Bartre's decent statline and suffered recoil after doubly-applied Fury, they are a fine choice.
• Chill Def passively lowers the Defense of an enemy with the highest in that stat, thus benefitting either Bartre or his teammates depending on the target.  

Preferred IV: +ATK or +SPD / -RES or -HP

• Due to a plethora of high-investment skills which offer a great amount of increased Speed, this stat is better worth considering as an Asset than ever. Dedicated investment in Speed allows Bartre to create new follow-up opportunities and generally come out victorious against opposing units in the base 30-45 range depending on skills run.   Attack, of course, is still solid especially for mid-level investment Bartre, or builds particularly focused on one-shotting.

Weapon: Axe of Virility (+Eff)

• For optimized offensive purposes, nothing else is better still than the effect refined Axe of Virility, which provides armor effectiveness and a free Fury on top of other offensive enhancements taken in other skill slots.
• The recoil suffered after combat also lends itself well to certain skills and combinations, including stacked Brazens, Wrath, Desperation, etc.

Assist: Reposition / Draw Back / Flexible

Special: Glimmer / Moonbow / Luna / Draconic Aura / Bonfire

• Glimmer and Moonbow are still ever-great choices as they provide good burst damage at low cooldown values.
• A Special with 3 cooldown activates less frequently than Moonbow and Glimmer, which helps Bartre save said Special for another priority target rather than activate in a single round. Luna, Draconic Aura, and Bonfire can be taken depending on your preference for reliability, Attack manipulation, or Defense manipulation respectively.

Passive A: Fury (3 or 4) / Swift Sparrow (2-3) / Atk/Spd Solo / Atk/Spd Bond / Brazen Atk/Spd (3 or 4) / Life and Death

• Bartre's base Fury is still great as ever as it provides additional raw stats on top of the ones Axe of Virility already provides, giving Bartre nice dual-phase performance. The recoil suffered from both also allows for safer activation of skills such as Wrath and Brazen skills.
• Swift Sparrow provides a straight Attack and Speed boost on initiation; its highest tier variant in particular offers the largest offensive boosts possible behind Brazen Atk/Spd.
• Atk/Spd Solo and Bond both provide rather substantial offensive boosts with the requirement of being non-adjacent to allies for the former, and the opposite for the latter.
• Brazen Atk/Spd takes setup, but said setup is very doable thanks to the Fury recoil from Axe of Virility as well as Bartre's nice survivability in physical matchups. After activation, Brazen Atk/Spd provides the largest potential offensive boosts possible in an A slot skill.
• Though Life and Death's defense drops make it a pretty odd option compared to the rest of the mentioned A-slot skills, this is cushioned by Fury's stat padding. Thus, in exchange for a solid +5 to Bartre's Attack and Speed, he only undergoes a mere net loss of -2 Defense and Resistance, the latter of which is pretty awful in the first place anyway.

Passive B: Null Follow-Up / Wrath / Lull Def/Spd / Lull Atk/Def / Desperation 

• Since many armored units are reliant on the Fighter skill line to achieve follow-up attacks, Null Follow-Up adds even more salt in the wound as the skill disables follow-up manipulation. Bartre can thus even more cleanly eliminate armored enemies without fearing otherwise deadly Fighter setups.
• Wrath excels on this build due Bartre's tendency to be at low health; it provides a substantial damage increase to his Special activations and passively charges his Specials outside of battle.
• A Lull skill of choice dulls the opponents' bonuses in their respective stats to zero, and further punishes them by an in-combat debuff of -3. This aids in creating gemera;;y better matchups and especially follow-up Attacks if a Spd-based Lull is taken.
• Desperation is a basic but fine option for builds superspecialized in Speed, allowing Bartre to make follow-up attacks immediately before the opponent can retaliate.

Passive C: Infantry Pulse / Panic Ploy / Flexible

• Due to Bartre's fantastic natural HP score and its resulting value after investment, Infantry Pulse is a great option that allows for potent precharge setups for his allies.
• Panic Ploy is also a good option as Bartre's HP usually one-ups those of the majority of enemies. However, due to the recoil suffered from certain skills as well as certain setups reliant on low HP, be mindful of its usage.
• The aforementioned skills are otherwise not particularly required, and the C slot skill is open for other options depending on budget and team preferences.

Sacred Seal: Brazen Atk/Spd / Sturdy Blow / Darting Blow / Flexible

• The recoil effect of Axe of Virility (and possibly Fury if taken) allows for easy activation of Brazen Atk/Spd, making Bartre even more offensively competitive.
• Sturdy Blow and Darting Blow are more immediate alternatives that boost an offensive stat of choice (Atk/Def for the former, Spd for the latter) on initiation.

Preferred IV: +ATK or +DEF / -RES

• A physically-inclined stat enhances the role this build is meant to do: take enemy attacks and dish a whole lot back. Attack is great for armorslaying scaling and builds focused on damage, whereas Defense substantially softens physical hits aimed at Bartre.
• Resistance plays virtually no role on this build and can easily be taken for the Flaw at zero merges.

Weapon: Axe of Virility (+Def) / Axe of Virility (+Eff)

• To maximize Bartre's raw survivability, Defense refinery for Axe of Virility may be considered over the effect refine for a few reasons: the Fury effect will wear down Bartre's health after every round of battle, and the added Speed and Resistance of said effect is irrelevant to this build. The Defense refinery grants a simple but meaty +5 HP and +4 Defense in comparison.
• For build switching flexibility and using skills centered on low HP activation, the effect refine is still worth regard as the Fury effect pads out all stats and inflicts beneficial recoil after every successful match.
• Regardless of refinery options chosen, Axe of Virility retains its armor effectiveness across all builds, making Bartre a quite fine choice for duking it out with melee armored enemies amongst other physical matchups.

Assist: Reposition / Swap / Flexible

Special: Aether / Ignis / Bonfire

• Great potential burst damage and sustain in one package make Aether a prime option above other options, though due to its impractical cooldown of 5, it requires cooldown acceleration (via Breath Skills, refined Geirskogul, Infantry Breath, or Infantry Rush).
• Ignis and Bonfire deal exclusively in damage dealing and have great damage potential due to scaling off of Bartre's great invested Defense. Due to a longer cooldown of 4, Ignis is recommended with cooldown acceleration, while Bonfire can be ran with or without.

Passive A: Steady Breath / Brazen Atk/Def / Fierce Breath / Steady Stance (3 or 4) / Fierce Stance / Atk/Def Bond  / Sturdy Stance

• A Breath skill of choice provides self-sufficient cooldown acceleration on both Bartre's and the enemy's attacks in enemy phase, allowing Aether and Ignis to activate at more practical timings. Steady or Fierce Breath are recommended in particular as they provide relevant in-combat stat booses in Defense and Attack, respectively.
• Brazen Atk/Def is an accessible but effective A slot especially for lower-HP setups. In particular, it pairs well with Wrath as it activates at nearly the same time.
• Steady Stance, Fierce Stance, and Sturdy Stance don't provide cooldown acceleration like their Breath equivalents but are otherwise solid and accessible choices with higher in-combat stats. Steady Stance 4 in particular provides the Guard effect, which eases matchups significantly against Special-reliant enemies.
• Atk/Def Bond provides similar in-combat buffs as Sturdy Stance in its respective stats. Though it requires adjacency, it has a higher payout and can work in player phase if Bartre must duke it out there for any reason.

Passive B: Quick Riposte / Wrath / Renewal / Guard

• This build isn't particularly invested in Speed, making Bartre naturally slower as a result. Quick Riposte is a nice fix to this as it provides a follow-up attack in enemy phase, as long as Bartre's HP remains over 70%.
• Wrath's passive Special charging and additional flat +10 damage to Special activations makes it a fine offensive option across most setups, especially those also employing Breath or Brazen skills.
• Renewal helps Bartre keep his own health intact in longer-winded matchups, especially in scenarios where he cannot rely on Aether or other means of recovery.
• Guard prevents enemies from charging their Special, or simply delays Special activation for those with a means of cooldown acceleration. This allows Bartre to safely tank Special-reliant enemies, especially Bold Fighter armors who in return get mauled by Axe of Virility.

Passive C: Panic Ploy / Infantry Pulse / Atk Smoke / Even Def Wave

• Bartre's fantastic resulting HP as a result of his great natural value, refinery, and general investment makes him a good candidate of skills such as Panic Ploy and Infantry Pulse.
• After a successful round of combat, Atk Smoke inflicts a harsh debuff of -7 Attack to surrounding enemies relative to his original target, thus making incoming onslaughts much more comfortable for tanking.
• A self-sufficient Defense or Attack buffing C slot, such as Even/Odd Defense Wave, give Bartre the flexibility to operate if away from teammates.

Sacred Seal: Atk/Def Bond / Quick Riposte / Close Def / Fierce Stance / Steady Stance

• In addition to the Attack and/or Defense fortifications offered by Axe of Virility and the A-slot skill, Atk/Def Bond further improves on the build's relevant stats. Its adjacency condition is easily fulfilled as the build will bait in enemy phase the majority of the time.
• If Quick Riposte is not taken in the B-slot, it is primarily recommended as the Sacred Seal as Bartre is barely able to perform second counterattacks otherwise.
• Other enemy phase-oriented Seals can be taken depending on availability and preferences.

Preferred IV: +HP or +ATK or +SPD / -RES

• A build focused on inflicting Panic and generally supporting rather than attacking directly prefers an Asset in HP. 
• For build-switching, however, Bartre's HP is already naturally high enough anyway to warrant using another Asset appropriate for other builds.  
• Since this is a high-investment build and thus benefits from merges, the Flaw disappears anyway.

Weapon: Axe of Virility (+Def) / Axe of Virility (+Eff)

• Axe of Virility's high SP cost makes the prime option, armor effectiveness is ideal for denting armors when needed. However, for those concerned with garnering bonus kills, exercise caution as the weapon may damage too much to the point of defeat.
• Defense refinery on Axe of Virility grants +5 additional HP as opposed effect refine's +3, making Panic skills slightly more potent. The difference between the two is relatively trifling, however; the effect refine can be taken for general self-effectiveness, flexible build switching (as the Fury effect is far better for offensive builds in particular), and tight use of your Divine Dew.

Assist: Rally Up Res+ / Rally Atk/Def+ / Flexible

• For scoring purposes, an Assist skill worth 600 (inherited) SP best maximizes Bartre's scoring potential. This can basically entail anything besides the listed Rally Up Res+ / Rally Atk/Def+, depending on your team needs and stat bonuses already covered through other means.

Special: Aether / Blue Flame / Shattered Sky

• A Special worth 750 (inherited) SP optimizes Bartre's scoring potential. The most easily accessible of this bunch is Aether, whose cooldown of 5 minimizes accidental non-bonus kills. If bonus kills is a non-issue, Bartre can instead take Blue Flame or Shattered Sky for a handy combination of low cooldown and great scoring in one. Notably, the native users of these skills also have other optimal skills to hand out, including Fury 4 and Wrath.

Passive A: G Duel Infantry

• In addition to increasing Bartre's normally-modest scoring bin of 156-160 to that of a 170 BST unit, G Duel Infantry also grants +5 HP, helping Bartre score even better while more effectively inflict Panic skills respectively.

Passive B: Sudden Panic / Chill Def / Chill Atk / Def/Res Ruse / Flexible

• Due to Bartre's near-godly HP value and Defense enemies' tendency to huddle up adjacently and constantly use Rally skills on each other, Sudden Panic is simply the bee's knees in terms of passive support Bartre can provide.
• A Chill skill of choice is another way Bartre can passively provide support; at the start of every turn, it inflicts a harsh debuff of -7 on an opposing superunit in the chosen stat.
• Depending on your budget and team needs, Bartre's B slot is host to other options. Honorary mention goes to Ruse skills as its dual stat debuffs and Guard infliction makes matchups even more troublesome for the opponent.

Passive C: Panic Ploy / Drive Res / Flexible

• As Sudden Panic only affects adjacent enemies with lower HP than Bartre, Panic Ploy can help Bartre affect enemies in cardinal directions instead.
• Another C skill can be taken—preferably with an SP cost of 240-300—if you'd like to use Panic Ploy as the Sacred Seal instead.  

Sacred Seal: Chill Def / Panic Ploy / Flexible

• The Sacred Seal can be open for useful skills not taken in previous slots; for instance, some Chill skill can be used if something else is in the B slot, and the same applies for Panic Ploy in the C slot. Otherwise, like the B and C slot skills, the Sacred Seal is up to the player.