It casts tier V elemental spells (long cast time; you can cast a bar spell easily).
Casts Absorb-TP, which absorbs TP from all nearby targets.
AOE damage + silence/paralyze.
Below 50% HP, has a much more powerful AOE damage skill.
Below 50% HP, can obtain physical+magical damage immunity. Ingrid will dispel this with Merciless Strike, accompanies by text in the chat log. It may still be debuffed while it has the damage immunity.
During this invincible phase, it will prefer to use Noahionto. It is advised to disengage and keep Ingrid healed until she can dispel his immunity.