Jakob

• Preferred IV: +SPD or +ATK / -HP or -DEF or -RES
• Weapon: Barb Shuriken+ (+Spd)
• Assist: Ardent Sacrifice / Draw Back
• Special: Moonbow / Luna
• Passive A: Life and Death / Swift Sparrow 
• Passive B: Desperation / Swordbreaker / Bowbreaker / G Tomebreaker
• Passive C: Drive Spd / Threaten Spd / Flexible
• Sacred Seal: Speed +3 / Attack +3

An offensive set utilizing the Barb Shuriken (or Kagami Mochi, if one wishes Jakob to serve mochi alongside his famous tea), centered around maximizing Jakob's Speed. Between his weapon refinement, A slot, Sacred Seal, and a Speed boon, Jakob reaches a passable Attack and Speed of 46 and 44, and this Attack heightens to an effective 53 on debuffed enemies. Swift Sparrow can be used instead of Life and Death to preserve his defenses at the cost of just a single point to both stats when initiating, though beware the loss of the Speed for Enemy Phase.

Ardent Sacrifice is paired alongside an HP bane to allow Jakob to reach Desperation range within a single use. If one lacks an HP bane or is willing to drop a bit of generalist power for some extra specialization, Ardent Sacrifice can be replaced with a movement assist such as Draw Back and Desperation can be replaced with a breaker of choice, ensuring doubles and safety against a specific class of foe. Swordbreaker, Bowbreaker, or G Tomebreaker are all decent options, depending on whom one wants him to specialize in fighting. 

Moonbow is Jakob's preferred Special, as with Barb Shuriken it will have a cooldown of just one, and so long as he doubles his opponent he will be able to activate it in every combat, even in Desperation range. Luna however is more powerful if used with a breaker and/or if one expects to take a counterattack.

Drive Spd is a great C skill that helps boost his allies, though virtually any Hone, Spur, or Drive can work just as well based on the needs of his teammates. While Jakob rarely aims to frontline, Threaten Spd can be useful as it can be applied quite safely on melee targets, some of which he may have difficulty outspeeding otherwise.

• Preferred IV: +SPD / -DEF or -RES
• Weapon: Smoke Dagger+ (+Spd) / Silver Dagger+ (+Spd)
• Assist: Rally Spd/Res / Reciprocal Aid / Draw Back
• Special: Luna / Miracle
• Passive A: Darting Blow / Fury 
• Passive B: Watersweep / Renewal 
• Passive C: Drive Spd / Drive Def 
• Sacred Seal: Drive Atk / Drive Def / Spur Spd

A relatively budget-friendly debuff & Spur set, aiming to make the most of the debuff effects of daggers. Smoke Dagger offers the most debuff potential if one can grant it to him, but otherwise his default Silver Dagger can suffice.

When not attacking, assists like Rally Spd/Res or Reciprocal Aid instead let Jakob continue to provide team support. Reciprocal Aid in particular synergies with Jakob's default Renewal skill, allowing him to fix up an ally in an emergency. Of course assists that move allies such as Draw Back are always safe picks.

Thanks to his poor Attack and mediocre bulk, Luna is the only Special that will provide Jakob with any significant damage. Miracle is a somewhat gimmicky for-fun alternative, completely forging a damage Special for the potential to survive a fatal hit. This can allow for some surprising bait and outplay potential, allowing him to safely lure an enemy to him that might normally KO him, and weaken them for any follow up next turn. 

Darting Blow is used to guarantee the success of Watersweep, especially if using just Watersweep 2, as even after a boon and refine Jakob's Speed still isn't insanely high. Fury is the common alternative, which also pads out Jakob's defenses and works well if using Renewal.

In order to remain useful after applying his debuffs, Drives and Spurs are recommended for Jakob's C skill and Sacred Seal, further boosting the stat swing created by his dagger for a choice ally to utilize. On a budget-friendly note, both Drive Spd 2 and Rally Spd/Res can be obtained from a single 4-star Tailtiu so long as he is given Spur Spd 1 first, which itself can be obtained from a Saizo when given Smoke Dagger+.

• Preferred IV: +SPD or +RES or +DEF / -HP or -DEF or -RES
• Weapon: Smoke Dagger+ (+Spd/Def/Res) / Barb Shuriken+ (+Spd/Def/Res)
• Assist: Rally Spd/Def / Reposition / Reciprocal Aid 
• Special: Bonfire or Iceberg / Ignis or Glacies
• Passive A: Distant Def / Fury
• Passive B: Quick Riposte / Bowbreaker / G Tomebreaker
• Passive C: Drive Spd / Drive Def / Atk Smoke
• Sacred Seal: Distant Def

A rather expensive set for huge Jakob lovers, here Jakob attempts to switch up his playstyle and make use of his mixed defenses by essentially emulating a "Distant Def 6" Guard Bow archer. With two instances of Distant Def, Jakob reaches a decent mixed defensive spread of 37/36 Def/Res, essentially 43/42 Def/Res after Smoke Dagger's Attack debuff, which lets him comfortably take both magical and physical ranged attacks. A Barb Shuriken is an alternative to Smoke Dagger to help him proc Specials faster, but will necessitate the use of Atk Smoke for tanking and does not debuff enemy Speed. If one believes his Speed won't cut it anyway, his boon and refine may instead be swapped to a defensive stat to instead push his raw bulk as far as possible.

With Jakob's defenses finally achieving some decent levels, Bonfire or Iceberg actually allow him to nuke enemies rather hard. Ignis or Glacies will give him even more burst, though will never activate in just one combat.

Quick Riposte will let him retaliate twice, and works to great effect on Enemy Phase sets such as this. Alternatively Jakob can utilize a breaker skill to give him a much easier time combatting a chosen ranged enemy type, such as an archer or green mage, which are some of the most frequently encountered in arena.

As Jakob is almost never initiating combat when utilized in this fashion, he can continue to go all in with his Assist and C slots to support his allies.