Nov 18, 2020, 13:5911/18/20
Hey
This is likely due to his passive:
"Frigid Vengeance [Passive] Attacks all enemies 1 time
whenever Klyssus’s HP drops below 80%, 60%, 45%, 30% and 15%. This
attack will revive any dead allies to 100% HP. This attack ignores 50%
of each enemy’s DEF for each alive ally. This attack also has a 20%
chance of placing a [Freeze] debuff for 1 turn. The chance of placing a
[Freeze] debuff increases by 40% for each alive ally."
Cheers