The Argosy Captain

When the Argosy Captain enters the battlefield,
put a trade counter on target creature.
Creatures with trade counters are merchants in addition to their other types.
Whenever one or more merchants deal combat
damage to a player, the defending player gains
twice that much life, and those creatures'
controller draws a card for every five ponts of
life gained this way.
{g}{w}{u}: Put a trade counter on target creature.