Resolving Geier Reach Sanitarium with Notion Thief in Play

Question

In a game of commander, if I have both Geier Reach Sanitarium and Notion Thief in play then activate Geier Reach's ability, my assumption is that the simplified explanation of the outcome would be: "I draw 4 cards, discard 1, and each of my opponents discard a card", but I want to understand the order of actions better.

The key thing I want to understand is, can I draw all 4 cards and then discard a card, or do I need to draw a card discard a card, then draw the additional three cards.

I know that as a replacement affect, Notion Thief's ability does not use the stack, but what is the order in which Geier Reach's ability resolves? If it requires priority order, I assume that if I am the active player I would have to draw 1, discard 1, then draw 3, but if I wait until the turn of the opponent who immediately follows me in turn order, can I draw 4 then discard 1? Or does the fact that I am activating the ability mean priority order always starts with me?

Answer 1

You draw all 4 cards and then discard 1.

Look at the following card-specific ruling on Geier Reach Sanitarium:

When you activate Geier Reach Sanitarium's last ability, first each player draws a card. Then the player whose turn it is selects a card from their hand and sets it aside without revealing it; proceeding in turn order, each other player does the same. Then the cards that were set aside are discarded at once.

This is then modified by Notion Thief's replacement effect to mean, effectively: first, you draw all the cards. Then, you discard, followed by each player in turn order.