yugioh monarch trap cards Yu-Gi-Oh! - Emperor of Darkness Structure Deck up monsters on the field The First Monarch

Note that there are no brakes here like "nontoken" this works for anything else that ETBs

There are of course some fantastic ways to play this and have it be genuinely powerful, mostly involving graveyard synergy or I win combos

If you didn't collect Kaldheim maybe you have these two synergistic cards on hand: Pelt Collector and Viridian Emissary

Reveal 1 "Neo-Spacian", "Elemental HERO" or Level 10 monster from your hand, Deck or Extra Deck, then this turn if you were to use the target as Fusion Material, you can treat its name as the revealed monster's name, also if "Elemental HERO Neos" is on your field or GY, send the revealed monster from your Deck to the GY, otherwise shuffle it from your hand into the Deck

It's basically a Doubling Season on a stick, but you don't see that card in anything except commander format