Valter

• Weapon: Cursed Lance
• Assist: Reposition / Movement Assist
• Special: Bonfire / Luna
• Passive A: Close Defense 3 / Defense +3 / Fury 3
• Passive B: Quick Riposte 3 / Vantage 3 / Drag Back
• Passive C: Panic Ploy 3 / Hone Fliers / Varies On Team
• Sacred Seal: Close Def 3 / Atk Smoke 3 / Iote's Shield 

With Valter's mixed bag of stats, there are plenty of ways to build and optimize the Dark Moonstone. His good DEF and HP combined with respectable ATK makes him a great defensive tank that can still pack a punch. For weapons, his exclusive Cursed Lance is just too good not to use, the stat bonuses and -1 special triggers makes the after combat damage well worth it. Reposition is generally the best way to go in terms of Supports, however, other options like Swap work perfectly, especially in Flier Emblem. Specials are a bit of a toss up for Valter. His base Luna works just fine and is perfect for dueling other tanks, but the damage gained from Bonfire is quite appealing for all-around use.

For A, B, and C skills there are many options to choose from. Close Defense 3 is excellent if you plan on using Valter primarily as physical tank, but if you're looking for a more budget option, Defense +3 works just fine. There has been plenty of discussion on whether or not Fury 3 should be considered as a viable choice for Valter. Combined with his Cursed Lance, you are essentially taking 10 after-combat damage or, in other terms, getting hit by Poison Strike 3. This damage CAN be synergized with skills like Desperation or Vantage, but is overall a risky pick. 

Quick Riposte, Vantage, and Drag Back are all useful options with their own benefits. Quick Riposte guarantees a double attack when getting attacked over 70% HP which can be useful when dealing with speedy melee units. Drag Back can be used to set up kills for your team, bringing enemy units into awkward spaces and can also be used to retreat. Finally, Vantage synergizes the best with Fury and is best utilized after combat with an enemy, but neither of you die.

C Slot skills are still the most flexible and Valter has access to one of the most sought after skills in the game currently, Panic Ploy. With his decent HP pool, Valter can reliably activate this skill to reverse enemy Hone and Fortify buffs, making them much either to deal with. Panic Ploy is most valuable when facing specific class based teams like Cavalry and Flier due to turning a +6/+6 buff, into -6/-6 penalties. 

• Weapon: Cursed Lance
• Assist: Reposition / Movement Assist
• Special: Draconic Aura / Luna
• Passive A: Life and Death 3 / Darting Blow 3 / Fury 3
• Passive B: Desperation 3 / Vantage 3 / Drag Back
• Passive C: Panic Ploy 3 / Hone Fliers / Varies On Team
• Sacred Seal: Speed +3

This build takes a different spin on Valter focusing on a more offensive, Player Phase oriented playstyle. As previously stated, Cursed Lance is too good to pass up on and separates Valter from other blue fliers like Tana and Cordelia. Reposition is standard, but can also be replaced with whatever Movement Assist you want, most notably Swap. Specials are a bit different this time since we're focusing less on defense and more on offense. Draconic Aura scales better with skills such as Life and Death 3 since there is a steep -5 DEF drop.

An offensive Valter is extremely similar to Minerva in both skills and stats. Life and Death 3 works well with Valter's fairly high ATK and SPD, and while the -5 DEF is a pretty big hit, the increase in kill potential makes up for it. Darting Blow 3 is a base skill for Valter and it's a great choice if you don't have the means to inherit Life and Death. Fury can also be used to throw Valter into Desperation or Vantage range, but receiving 10 damage each time you exit combat is still incredibly risky.