Escalation of the Monarchs

Continuous Trap

Once per turn, during your opponent's Main Phase or your opponent's Battle Phase, you can: Immediately after this effect resolves, Tribute Summon 1 monster.

Rulings – Yugipedia

Printings:

Primal Origin: PRIO-EN089 (Super Rare) - 2014-05-16
2015 Mega-Tin Mega Pack: MP15-EN054 (Super Rare) - 2015-09-17
Emperor of Darkness Structure Deck: SR01-EN036 (Common) - 2016-01-28

Prices:

Cardmarket: 0.22 €
TCGplayer: $ 0.37