Deadly Poison

Enchant creature
You may cast Deadly Poison without paying its
mana cost if target a rogue.
Whenever enchanted creature deals combat
damage to a player, put a poison counter on
Deadly Poison. At beginning of your turn,
Deadly Poison deals X damage to that player,
where X is the number of poison counters on it.
When enchanted creature attacks another player,
remove all poison counters of Deadly Poison.