The following material is Open Game Content from the Menace Manual SRD
Damage Reduction 20/+1 (Su): A montauk monster ignores the first 20 points of damage dealt by any nonmagical weapon. In campaigns without magic weapons, the GM can either disregard the montauk monster’s damage reduction or apply it only to certain types of weapons (ballistic, bludgeoning, piercing, slashing, or sonic/concussion).
Elemental: Montauk monsters have all the traits common to elementals.
Energy Claw (Ex): In addition to its base damage, a Montauk monster’s claw attack deals 1d6 points of electricity damage and 1d6 points of fire damage with a successful hit.
Energy Form (Ex): Montauk monsters are raw energy given sentience. Their bodies and their melee attacks are force effects.
Fast Healing 3: A montauk monster heals 3 points of damage per round unless it is reduced to –10 or fewer hit points. This ability does not enable a montauk monster to regrow or reattach severed body parts.
Fire Subtype (Ex): A montauk monster is immune to fire damage and takes 50% more damage from cold attacks.
Fuse (Su): Once every 1d4 rounds, a montauk monster can cause a creature it has successfully hit with a melee attack to fuse with nearby matter. At the time of the attack, the target creature must be within 5 feet of a solid object with a volume at least equal to its own. (In most cases, the ground or a wall is sufficient.) The target must succeed at a Will saving throw (DC 10 + 1/2 the montauk monster’s Hit Dice + its Charisma modifier) or be fused with the object and instantly killed. The object’s hardness drops by 2 after the fusion, regardless of the creature’s nature or physical makeup. Such an object continues to function normally, but it is usually cosmetically grotesque, with fleshy fingers or a portion of a face projecting from its surface.
Immunities (Ex): Montauk monsters are immune to fire and electricity. They are also immune to force effects such as mage armor, magic missile, and wall of force. The creatures and their melee attacks pass through such effects unharmed and unhindered.
Invisibility (Su): A montauk monster is naturally invisible, as though constantly under the effect of the invisibility spell (caster level 10th). Like a subject of that spell, the monster becomes visible upon attacking, but it can reinstate its invisibility as a free action once per round.
Montauk Monster: CR 11; Large elemental (air, fire); HD 9d8+27; hp 67; Mas —; Init +1; Spd 30 ft.; Defense 14, touch 10, flat-footed 13 (–1 size, +1 Dex, +4 natural); BAB +6; Grap +16; Atk +11 melee (1d8+6 plus 1d6 fire plus 1d6 electricity, energy claw); Full Atk +11 melee (1d8+6 plus 1d6 fire plus 1d6 electricity, 2 energy claws); FS 10 ft. by 10 ft.; Reach 10 ft; SQ damage reduction 20/+1, darkvision 60 ft., elemental, energy claw, energy form, fast healing 3, fire subtype, fuse (DC 15), immunities, invisibility; AL evil; SV Fort +6, Ref +9, Will +3; AP 0; Rep +0; Str 22, Dex 13, Con 16, Int 6, Wis 10, Cha 12.
Skills: Climb +13, Listen +9, Move Silently +8, Spot +9.
Feats: Alertness, Lightning Reflexes.
Advancement: 10–18 HD (Large); 19–27 (Huge).
Advanced Montauk Monster: CR 14; Huge elemental (air, fire); HD 19d8+95; hp 180; Mas —; Init +0; Spd 30 ft.; Defense 15, touch 8, flat-footed 15 (–2 size, +7 natural); BAB +14; Grap +32; Atk +22 melee (2d6+10 plus 1d6 fire plus 1d6 electricity, energy claw); Full Atk +22 melee (2d6+10 plus 1d6 fire plus 1d6 electricity, 2 energy claws); FS 15 ft. by 15 ft.; Reach 10 ft; SQ damage reduction 20/+1, darkvision 60 ft., elemental, energy claw, energy form, fast healing 3, fire subtype, fuse (DC 24), immunities, invisibility; AL evil; SV Fort +11, Ref +13, Will +6; AP 0; Rep +0; Str 30, Dex 11, Con 20, Int 6, Wis 10, Cha 12.
Skills: Climb +22, Listen +14, Move Silently +12, Spot +14.
Feats: Alertness, Combat Reflexes, Lightning Reflexes, Power Attack.