Golgari Grave-Troll

Once you've announced that you're applying a card's dredge ability to replace a draw, players can't take any actions until you've put that card into your hand and milled cards.

Dredge can replace any card draw, not only the one during your draw step.

If you return Golgari Grave-Troll from your graveyard directly to the battlefield, its first ability counts itself.

Because damage remains marked on a creature until it's removed as the turn ends, nonlethal damage dealt to Golgari Grave-Troll may become lethal if you remove +1/+1 counters from it during that turn. In this case, it dies before you can resolve the activated ability that will regenerate it.