A nightcrawler is a massive behemoth similar to a purple worm, though utterly black in color.
A nightcrawler measures about 7 feet in diameter and is 100 feet long from its toothy maw to the tip of its stinging tail. It weighs about 55,000 pounds.

A nightcrawler attacks by burrowing through the ground and emerging to strike.
A nightcrawler?s natural weapons are treated as magic weapons for the purpose of overcoming damage reduction.
Energy Drain (Su): Living creatures inside a nightcrawler?s gizzard gain one negative level each round. The DC is 26 for the Fortutude save to remove a negative level. The save DC is Charisma-based.
For each such negative level bestowed, the nightcrawler gains 5 temporary hit points.
Improved Grab (Ex): To use this ability, a nightcrawler must hit with its bite attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can try to swallow the opponent in the following round.
Poison (Ex): Injury, Fortitude DC 22, initial and secondary damage 2d6 Str. The save DC is Consitution-based.
Spell-Like Abilities: At will?contagion (DC 18), deeper darkness, detect magic, greater dispel magic, haste, invisibility, see invisibility, unholy blight (DC 18); 3/day?cone of cold (DC 19), confusion (DC 18), hold monster (DC 19); 1/day?finger of death (DC 21), mass hold monster (DC 23), plane shift (DC 21). Caster level 25th. The save DCs are Charisma-based.
Summon Undead (Su): A nightcrawler can summon undead creatures once per night: 9?16 shadows, 3?6 greater shadows, or 2?4 dread wraiths. The undead arrive in 1d10 rounds and serve for 1 hour or until released.
Swallow Whole (Ex): A nightcrawler can try to swallow a grabbed opponent of Huge or smaller size by making a successful grapple check. Once inside, the opponent takes 2d8+12 points of bludgeoning damage plus 12 points of acid damage per round from the nightcrawler?s gizzard and is subject to the creature?s energy drain. A swallowed creature can cut its way out by usining light slashing or piercing weapon to deal 35 points of damage to the gizzard (AC 21). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out. A nightcrawler?s interior can hold 2 Huge, 8 Large, 32 Medium, 128 Small, 512 Tiny or smaller opponents.

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System Reference Document -> List of Creatures (SRD)