Marchesa's Emissary

Oracle Text

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Dethrone (Whenever this creature attacks the player with the most life or tied for most life, put a +1/+1 counter on it.)

Card Rulings

5/29/2014 Dethrone doesn’t trigger if the creature attacks a planeswalker, even if its controller has the most life.
5/29/2014 Once dethrone triggers, it doesn’t matter what happens to the players’ life totals before the ability resolves. You’ll put a +1/+1 counter on the creature even if the defending player doesn’t have the most life as the ability resolves.
5/29/2014 The +1/+1 counter is put on the creature before blockers are declared.
5/29/2014 In a Two-Headed Giant game, dethrone will trigger if the creature attacks either player on the team with the most life or tied for the most life.