The dredge ability seems a lot like a trigger, but it’s not — it’s a replacement effect that modifies the event of drawing a card. Which means it’s probably not a good idea to try to use other replacement effects to stop your opponent from dredging. For example, if you control a Notion Thief, don’t expect to be drawing any cards soon. When your opponent tries to resolve an effect that would let her draw a card, such as Cephalid Coliseum, both replacement effects jump in and say “pick one!” to your opponent (the affected player). Your opponent will probably choose the dredge effect, which means there’s no longer any draw for Notion Thief to replace.
Perhaps you can stop your opponent from drawing entirely? Spirit of the Labyrinth, for example, prevents your opponent from drawing any cards at all after the first card each turn. This is great if you can somehow trick your Dredge opponent into drawing a card. However, if she replaces each of her draws with dredges, the Spirit never sees that she actually drew a card — and therefore won’t stop her from replacing her prospective card draws with further dredges. Of course, if she draws her first card normally under Spirit of the Labyrinth, then tries to dredge from a later draw, that won’t work because the second draw effect won’t be possible.
If you want to shut off dredging entirely, you’ll need an effect that says players “can’t draw cards,” like Maralen of the Mornsong or Omen Machine. On second thought… you could just play cards that exile their graveyard instead, like Tormod’s Crypt.
Today’s Rules Tip written by Jen Wong