Blue Fest. King (Full Wing): For the shield and to convert buffs to debuffs on enemies.
Blue Fest. Luciodel: For damage reduction and damage increase, further helping my team tank enemies' attacks.
Red Gowther: For rank ups and attack seals
Red Purgatory Ban: For BIG damage on green enemies with max hp damage.
Sariel is for King because of the Grace that ignores 50% of crit defence
Tarmiel is for Ban because of the healing.
King for Gowther for the ultimate.