What a coincidence the source that I found the thallid happened to have your fav too.
Thallid Devourer
Large (Long) Plant
Hit Dice: 5d8+10 (32 hp)
Initiative: +1 (+1 Dex)
Speed: 20 ft
AC: 18 (+1 Dex, -1 Size, +8 Natural)
Attacks: 1 Slam +7 melee, 1 Bite +2 melee
Damage: Slam 1d6+3, Bite...