Libra

Weapon: Inviolable Axe (+Eff)

Assist: Positional Assist / flexible

Special: Ruptured Sky / Moonbow / flexible

IVs: +Spd or +Atk / -Res

Passive A: Atk/Spd Unity / Atk/Def Unity / Kestrel Stance / flexible

Passive B: Spurn / Null Follow-Up / Null C-Disrupt

Passive C: Joint Drive Spd / Joint Drive Atk / flexible

Sacred Seal: Darting Breath / Atk/Spd Bond / flexible

• With an overall balanced statline, Libra can function decently well as a tank, particularly against melee units if he does not need to use Distant Counter or a similar skill. Libra benefits heavily from some support units on this build. If using a support such as Flayn, Elimine, or Nifl that provides damage reduction, Libra can opt for Null Follow-Up in order to disable guaranteed enemy follow-up attacks, improving his matchups substantially. Alternatively, if he has Null Follow-Up support from Legendary Male Byleth, he prefers to use a skill like Spurn to gain damage reduction up to 40%. Null C-Disrupt can also be useful to allow him to counter effects like Firesweep weapons and similar, but is generally a less useful choice compared to the other two listed options. Without these or other useful support units, Libra will struggle against some common melee foes like Legendary Sigurd. 
• Darting Breath seal allows Libra to gain extra charge on all attacks when he is attacked. This allows him to get hit once and immediately retaliate with a 2-cooldown Special like Ruptured Sky or Moonbow, potentially KOing opponents with lower Def and HP. 
• Something similar to this build can be used with Distant Counter or a similar skill in order to allow Libra to counterattack units at all ranges. However, he loses the stats and effects from an A skill by doing so, and will struggle in some modes as Libra’s statline is already not amazing. 

Weapon: Inviolable Axe (+Eff)

Assist: flexible / unimportant

Special: Moonbow / Noontime / flexible

IVs: +Spd or +Atk / -Res

Passive A: Surge Sparrow / HP +5 / flexible

Passive B: Spurn / Null Follow-Up / Null C-Disrupt

Passive C: Joint Drive Spd / Joint Drive Atk / Savage Blow / flexible

Sacred Seal: Blade Session / HP +5 / flexible

• Inviolable Axe’s healing effect gives Libra a somewhat unique role in Pawns of Loki, the mode where scoring is affected by each unit on the team’s HP at the end of each round. While he isn’t the most capable unit when it comes to dealing damage, he does have solid utility as a healer. As staff units will not use assist skills in Pawns of Loki, healing is harder to come by, and Libra is more useful. 
• The skills are chosen to generally improve Libra’s damage dealt, reduce damage taken, or the player can instead opt for HP boosts in the A and S slots in order to improve Pawns of Loki scoring. Skills like Surge Sparrow and Null Follow-Up will improve his ability to damage enemy units while remaining at high HP. However, these are not necessary in order for him to fulfill the basic role of healing, and the player may in fact benefit more from the HP boost to scoring if playing on Intermediate difficulty or below.