Suppose I have Sidisi, Brood Tyrant out:
Whenever one or more creature cards are put into your graveyard from your library, create a 2/2 black Zombie creature token.
I also have Underrealm Lich:
If you would draw a card, instead look at the top three cards of your library, then put one into your hand and the rest into your graveyard.
I then play Concentrate:
Draw three cards.
Because of rule 120.2, I do this by drawing one card three times, each of which is replaced by Underrealm Lich's replacement effect:
120.2. Cards may only be drawn one at a time. If a player is instructed to draw multiple cards, that player performs that many individual card draws.
So, three times I will look at the top three cards of my library, put one into my hand, and put the rest into my graveyard.
Let's assume for simplicity that every card near the top of my library is a creature card. In this situation, does Sidisi create:
- only one zombie, because of the single "draw three cards" instruction putting creature cards into my graveyard, or
- three zombies, because of three separate instructions from Underrealm Lich putting creature cards into my graveyard?