Boss Rush

Continuous Spell

You cannot Normal Summon or Set. During the End Phase of the turn that a "B.E.S." monster or a "Big Core" is destroyed and sent to the Graveyard, you can Special Summon 1 "B.E.S." monster or 1 "Big Core" from your Deck.

Rulings – Yugipedia

Printings:

Elemental Energy: EEN-EN047 (Common) - 2005-11-16
Dark Revelation Volume 4: DR04-EN107 (Common) - 2007-11-14
OTS Tournament Pack 30: OP30-EN017 (Common) - 2026-02-12

Prices:

Cardmarket: 0.05 €
TCGplayer: $ 0.20