Inspiration from good old d20 Modern. Thought they were more interesting than “another ooze” which The Divinity Drive seems to have an excessive number of.
NUCLEAR TOXYDERM (MAJOR)
Large elemental, neutral
Armour Class 18 (natural armour)
Hit Points 350 (21d20+147)
Speed 0 ft., fly 60ft.
STR 30 (+10) DEX 11 (+0) CON 24 (+7)
INT 8 (-2) WIS 8 (-2) CHA 1 (-5)
Damage Resistances bludgeoning, piercing, and slashing from nonmagical weapons
Damage Immunities poison, radiation
Condition Immunities exhaustion, grappled, paralysed, petrified, poisoned, prone, restrained, and unconscious
Senses darkvision 60ft., passive Perception 10
Challenge 16 (15,000 XP)
Fallout. The nuclear toxyderm can enter a hostile creature’s space and stop there. It can move through a space as narrow as 1 inch wide without squeezing. Creatures in the same space are automatically exposed to high radiation.
Mutagenic Agent. Remember creatures exposed to radiation poisoning have a chance of gaining a mutation
Multiattack. The nuclear toxyderm makes one slam attack. However it may use radioactive fire and nuclear slag whenever available.
Slam. Melee Weapon Attack: +15 to hit, reach 15 ft., one target.
Hit: 22 (4d6 + 10) bludgeoning damage plus 36 radiation (18 (4d8) poison and 18 (4d8) fire) damage, and the target is grappled (escape DC 18). Until this grapple ends, the target is restrained, and automatically takes slam damage at the start of its turn. The toxyderm can’t crush another target however it may continue to make slam attacks.
Radioactive Fire (On a natural 18+). In addition to its slam attack it shoots 1d4 rays at random (separate) targets. No more than one ray per target.
Radioactive Ray. Range Natural Weapon Attack: +5 to hit, range 60 ft., one target
Hit: 36 radiation (18 (4d8) poison and 18 (4d8) fire) damage.
Nuclear Slag (Recharge 6). The toxyderm exhales a blast in a 60-foot cone. Each creature in that area must make a DC 21 Dexterity saving throw, taking 66 (12d10) radiation (poison and fire) damage on a failed save and being exposed to high radiation, or half as much damage on a successful one and no radiation exposure.
Chain Reaction. Each creature within 20 feet radius of the nuclear toxyderm’s space must make a DC 18 Dexterity saving throw. On a failure, a target takes 36 radiation (18 (4d8) poison and 18 (4d8) fire) damage and is flung up to 20 feet away from the toxyderm in a random direction and knocked prone. Objects are also damaged by this blast and radiation immunity is considered to be resistance in the case of chain reaction damage. If a thrown target strikes an object, such as a wall or floor, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 15 Dexterity saving throw or take the same damage and be knocked prone. The target is also exposed to high radiation poisoning. If the saving throw is successful, the target takes half the radiation damage, is exposed to only medium radiation poisoning, and isn’t flung away or knocked prone. The explosion will result in a mushroom cloud and leave a radioactive crater in the blast radius.
The most feared species of toxyderm these creatures arise from accumulations of low-level nuclear waste. They look like vaguely quadrupedal masses of glowing, burning slag.