Necrosynthesis
From Innistrad: Midnight Hunt set
Necrosynthesis
Enchantment — Aura
Enchant creature
Enchanted creature has "Whenever another creature dies, put a +1/+1 counter on this creature."
When enchanted creature dies, look at the top X cards of your library, where X is its power. Put one of those cards into your hand and the rest on the bottom of your library in a random order.