Guardian Kay'est

Level 4 WATER/Sea Serpent Effect Monster
1000 ATK / 1800 DEF

Cannot be Summoned unless you control a face-up "Rod of Silence - Kay'est". This card is unaffected by Spell effects and cannot be targeted for attacks, but does not prevent your opponent from attacking you directly.

Rulings – Yugipedia

Printings:

Dark Crisis: DCR-009 (Common) - 2003-12-01
Dark Crisis: DCR-EN009 (Common) - 2003-12-01
Dark Revelation Volume 1: DR1-EN171 (Common) - 2005-03-19
Legendary Collection 3: Yugi's World Mega Pack: LCYW-EN133 (Common) - 2012-09-29

Prices:

Cardmarket: 0.07 €
TCGplayer: $ 0.14