Punishment is Harrow’s game. He is able to bestow powerful buffs and effects on himself and his allies by killing enemies and absorbing damage.
Harrow’s passive is Conviction. Harrow has an overshield capacity larger than other warframes.
Ability Strength mods affect the amount of shields restored, per target, of Condemn, the amount of health restored, the attack speed and reload speed bonuses of Penance, the amount of energy gained while channeling Thurible and the base critical chance and damage to critical chance conversion ratio of Covenant. Ability Range mods affect the wave distance and size of Condemn and the aura radius of Thurible. Ability Duration mods affect the chain duration of Condemn, the duration of Penance and Thurible and the duration of both the invulnerability and retaliation phases of Covenant.
So, all things considered, here are some builds you may want to try on your Harrow: