Or:

Artifact

: The owner of this permanent draws a card and gets two poison counters. Any player may play this ability.
If you did that then your opponent only has to spend ten mana over any number of turns to kill you, provided you don't use it. Seems kind of crappy.
You can activate this a bunch of times then sacrifice it to avoid getting the counters. Seems kind of imba.
Just change the ability to:
2: Draw a card and you gain two poison counters. Any player may play this ability.
It's still really good.