Obsessive Pursuit (Showcase) [Avatar: The Last Airbender]

When this enchantment enters and at the beginning of your upkeep, you lose 1 life and create a Clue token.
Whenever you attack, put X +1/+1 counters on target attacking creature, where X is the number of permanents you've sacrificed this turn. If X is three or greater, that creature gains lifelink until end of turn.