Amabie reference art (OCG/TCG and Rush Duel versions)

Rush Duel:

Amabie (アマビエ) is a legendary Japanese mermaid or merman with a bird beak-like mouth and three legs or tail-fins, who allegedly emerges from the sea, prophesies either an abundant harvest or an epidemic, and instructed people to make copies of its likeness to defend against illness.

Via Wikipedia

Amabie was given away as a promo for participating in remote duels during 2021 after in-person play was shut down due to COVID-19