Only one creature because the card doesn't say "sacrifice any number of creatures."
Because the card must be tapped to be activated it can't be repeated multiple times a turn like Bloodthrone Vampire
Because the card says "sacrifice a creature" you cannot sacrifice multiple creatures, unlike something with devour ( Caldera Hellion )
April 27, 2019 4:45 p.m.
The cost of activating Culling Dais ' first ability is to tap the Dais, and to sacrifice a single creature. You can't overpay a cost by sacrificing more than one creature, just like you can't purposely pay more than three mana for Radiant Flames just to get a better Converge result.
You will need a way to untap the Dais in order to sacrifice more than one creature per turn.
April 27, 2019 7:36 p.m.
In the future, please remember to hit the “Mark as Answer” button once your question has been resolved. As this thread has been answered for several days, I’ve gone ahead and marked an answer on your behalf.