Dredge

[toastani]

The rule book doesn't specify whether or not you can dredge more than one card at a time. I always thought that it was just one card. an I right?

[adventus]

Any time you would draw 1 card you may use 1 dredge card in your graveyard.  It's a replacement effect.  You can only do it again if you're drawing another card with something like {howling mine} or {think twice}.

Here's a dredge card for reference: {Golgari Grave-Troll}.