Sea Dragon Lord Gishilnodon

Level 5 WATER/Sea Serpent Synchro Effect
2300 ATK / 1800 DEF

1 Tuner + 1 Level 3 non-Tuner monster
When a face-up Level 3 or lower monster on the field is sent to the Graveyard, this card's ATK becomes 3000 until the End Phase of this turn.

Rulings – Yugipedia

Printings:

Raging Battle: RGBT-EN044 (Super Rare) - 2009-05-12

Prices:

Cardmarket: 5.32 €
TCGplayer: $ 9.48