Acid (Ex): A toxic sludge is composed of caustic chemicals that dissolve any substance except stone and metal. A toxic sludge’s slam attack deals 1d4 points of acid damage in addition to the normal bludgeoning damage.
Blindsight (Ex): A toxic sludge is blind but can ascertain all creatures and objects within 40 feet just as a sighted creature would. Beyond that range, all targets have total concealment with respect to the toxic sludge.
Expansion (Ex): A toxic sludge absorbs the bodies of creatures it has killed in battle. This process takes a number of rounds depending on the size of the corpse: Diminutive or smaller 1, Tiny 2, Small 4, Medium-size 8, Large 16, Huge 32, Gargantuan 64, and Colossal 128. The sludge grows by 1 Hit Die for every 16 rounds it spends consuming bodies, to a maximum of 45 Hit Dice.
Immunities (Ex): Toxic sludges are immune to acid, electricity, and cold damage. If a cold attack deals damage equal to or greater than a toxic sludge’s Constitution score, the toxic sludge is affected as though by a slow spell.
Improved Grab (Ex): To use this ability, the toxic sludge must hit an opponent at least one size category smaller than itself with its slam attack. If it gets a hold, it automatically deals slam damage each round that the hold is maintained, and it can constrict in the same round.
Ooze: A toxic sludge has the traits and immunities common to oozes.
Toxic Fumes (Ex): Any creature that comes within 10 feet of a toxic sludge must make a successful Fortitude save (DC 10 + 1/2 the toxic sludge’s Hit Dice + its Constitution modifier) or take 1d4 points of Strength damage. A new save must be made each round a creature remains within 10 feet of the toxic sludge.
Toxic Sludge: CR 7; Large ooze; HD 6d10+27; hp 60; Mas —; Init –2; Spd 20 ft.; Defense 7, touch 7, flat-footed 7 (–1 size, –2 Dex); BAB +4; Grap +10; Atk +5 melee (1d8+3, slam plus 1d4 acid); Full Atk +5 melee (1d8+3, slam plus 1d4 acid); FS 10 ft. by 10 ft.; Reach 10 ft.; SQ acid, blindsight, constrict, expansion, immunities, improved grab, ooze, toxic fumes (DC 15); AL none; SV Fort +4, Ref +0, Will –3; AP 0; Rep +0; Str 15, Dex 7, Con 14, Int —, Wis 1, Cha 1.
Advancement: 6–12 HD (Large); 13–18 HD (Huge); 19–31 HD (Gargantuan); 32–45 HD (Colossal).
Advanced Toxic Sludge: CR 12; Gargantuan ooze; HD 20d10+150; hp 260; Mas —; Init –2; Spd 20 ft.; Defense 10, touch 3, flat-footed 10 (–4 size, –3 Dex, +7 natural); BAB +15; Grap +37; Atk +21 melee (2d8+10 plus 1d4 acid, slam); Full Atk +21/+16/+11 melee (2d8+10 plus 1d4 acid, slam); FS 20 ft. by 20 ft.; Reach 15 ft.; SQ acid, blindsight, expansion, immunities, improved grab, ooze, toxic fumes (DC 26); AL none; SV Fort +12, Ref +3, Will +1; AP 0; Rep +0; Str 31, Dex 5, Con 22, Int —, Wis 1, Cha 1.