This pile of steaming compost is very stinky and moving around...
CR 6; XP 2,400
NE Huge Undead
Init +0; Senses blindsight 30 ft.; Perception +1
Aura stench (DC 16; 10 rounds)
AC 18, touch 8, flat-footed 18 (+10 natural, –2 size)
hp 66 (12d8+12)
Fort +5, Ref +4, Will +9
Defensive Abilities amorphous, heat of decay; DR 5/—; Immune undead traits
Speed 20 ft., burrow 20 ft.
Melee 3 slams +12 (1d8+5)
Space 15 ft.; Reach 10 ft.
Special Attacks nauseating demise, nauseating strike
Str 20, Dex 10, Con —, Int —, Wis 13, Cha 13
Base Atk +9; CMB +16; CMD 26 (can't be tripped or bull-rushed)
SQ compression, devour plants
Environment temperate and tropical forests and plains
Organization solitary, pair, or pile (3–6)
Devour Plants (Ex) A compostnic can consume remains of a dead plant creature by spending a number of rounds equal to the creature's HD, regaining 2 hit points each round.
Heat Of Decay (Ex) Decaying core of a compostnic is very hot, adding 1d6 points of fire damage to its melee attacks on confirmed critical hits. When a compostnic is subject to any fire damage it emits acrid smoke that acts like a smoke cloud effect of pyrotechnics spell (saving throw DC 16), lasting 1 round. The saving throw DC is Constitution-based.
Nauseating Demise (Ex) When a compostnic is reduced to 0 or less hit points, it explodes in a shower of filthy, decaying plant matter. All the creatures within 10 feet of destroyed compostnic that fail a Fortitude saving throw (DC 16) become nauseated for 1d4+1 rounds. The saving throw DC is Constitution-based.
Nauseating Strike (Ex) When a creature suffering from sickened condition is hit with a compostnic's slam attack, it becomes nauseated for 1 round unless it makes a successful Fortitude saving throw (DC 16). The saving throw DC is Constitution-based.
Majority of the undead entities arise from dead people or beasts, but compostnics are little more than a pile of decomposed plant matter animated by negative energy. They are occasionally created by necromancers interested in gardening and plant creatures, those who have to utilize corpses of plant creatures, and corrupted druids.
To create a compostnic, a necromancer has to gather a significant amount of shredded decaying remains of plant creatures (approximately 10,000 pounds), supplemented with inanimate but expensive plants worth no less than 600 gp (or 50 gp per HD of created compostnic). Once the pile is ready, it needs to be targeted with either blight or diminish plants spell, followed by animate dead (the expensive plants replace the regular material component) with a minimum caster level 6th (or half the compostnic's HD).