Current Versions can be seen here.
Big Mouth is a card added in Beta 6.6, along with 19 others. It hasn't gone through any major changes yet. The only change it got was during Beta 7.1, where its cost dropped to 5G.
- 6 (Post Beta 6.6)
- 5 (Post Beta 7.1, Current)
Ability: Kill every summoned enemy monster (cost <= 2) and restore its HP.
Rarity: Blue (Rare)