Number Wall

Continuous Trap

Activate only if you control a "Number" monster. "Number" monsters on the field cannot be destroyed by card effects, and cannot be destroyed by battle except with another "Number" monster. When a "Number" monster you control is destroyed, destroy this card.

Rulings – Yugipedia

Printings:

Number Hunters: NUMH-EN058 (Secret Rare) - 2013-07-12

Prices:

Cardmarket: 1.26 €
TCGplayer: $ 1.14