Vorthropod

Lava Bound. Can exist outside of lava or magma for up to 4 hrs each day. If it starts its turn outside of lava and didn't take fire since end of its previous turn its shell begins to cool and harden. While its shell is hardened has walking speed of 20' AC 18 and vulnerability to bludgeoning. If it starts its turn in lava or if it took fire damage since end of its previous turn its shell becomes molten again. If vorthropod remains outside of lava for more than 4 hrs its shell becomes petrified transforming into basalt and vorthropod within goes into hibernation. Its body returns to normal if it is submerged in lava or magma for 1 round. It can stay petrified in hibernation for up to 1d100+10 years after which it dies.

Lava Camouflage. Has advantage on Dex (Stealth) checks made to hide in lava and volcanic terrain.

Molten Shell. If Its shell isn't hardened creature that touches it or hits it with melee attack while within 5 ft. of it takes 7 (2d6) fire.

Multiattack. Two Claw attacks.

Claw. Melee Weapon Attack: +6 to hit, 5 ft., one target, 8 (2d4+3) bludgeoning damage + 7 (2d6) fire.

Molten Tail Slap (Recharge 4-6). Unfurls its tail and slaps it down showering area with searing sparks and superheated rock. Each creature within 15 ft. of it: 28 (8d6) fire (DC 14 Dex half).