The Necrobloom

Once you've announced that you're applying a card's dredge ability to replace a draw, players can't take any action until you've put that card into your hand and put the top cards of your library into your graveyard.

If you control multiple lands with the same name, only one of those lands will count toward the seven or more required to create a Zombie. For example, if you control four lands named Forest, two named Plains, and one named Swamp, you control three lands with different names.

Dredge can replace any card draw, not just the one during your draw step. One card draw can't be replaced by multiple dredge abilities.

If an effect puts a card into your hand without specifically using the word "draw," you're not drawing a card. Dredge can't replace this event.

If multiple lands enter the battlefield under your control simultaneously, all of those lands are counted. For example, if you sacrifice seven lands while resolving Scapeshift and search your library for seven lands with different names, you'll create seven Zombie tokens.

If you're drawing multiple cards, each draw is performed one at a time. For example, if you're instructed to draw two cards and you replace the first draw with a dredge ability, another card with a dredge ability (including one that was put into your graveyard by the first dredge ability) may be used to replace the second draw.