When you take damage from a card your opponent controls while you control no cards, you can Special Summon this card from your hand. Then activate the appropriate effect, based on the type of damage:
? Battle Damage: Special Summon 1 "Emissary of Darkness Token" (Fairy-Type/LIGHT/Level 7/ATK ?/DEF ?). Its ATK and DEF are each equal to the amount of battle damage you took.
? Effect Damage: Inflict damage to your opponent equal to the amount of damage you took.