Not the best trap, but not even the worst (I consider Ithilien Pit to be that). It can be quite effective against some of those enemies which have a high and low hit points or even for those which rarely leave the staging area (both for high engagmente cost or other effects). Of course as with almost all the other traps it's the strongest if it's combined with some encounter deck scrying/manipulation.
Attachment. Cost: 2.
Play Poisoned Stakes into the staging area unattached.
If unattached, attach Poisoned Stakes to the next eligble enemy that enters the staging area.
At the end of each round, deal 2 damage to attached enemy.
The Blood of Gondor #115. Lore.