Baleful Miasma 2014
CR 2 elemental
Medium elemental, neutral evil
Can enter a hostile creature’s space and stop there. Can move through space as narrow as 1ft. wide with o squeezing.
If a creature that breathes air starts its turn in miasma’s space it must make DC 12 Con save or begin suffocating as its lungs fill with the poisonous air emitted by the miasma. Suffocation lasts until creature ends its turn in a space not occupied by baleful miasma or the baleful miasma dies. When the suffocation ends the creature is poisoned until the end of its next turn.
Doesn’t require air food drink or sleep.
Reactions
If a creature in same space as miasma moves miasma can move up to its speed with the creature. This move doesn't provoke opportunity attacks but miasma must move in same spaces creature moved ending in creature's space or space nearest to it.
Source: Tome of Beasts 3 (Kobold Press) · License: OPEN GAME LICENSE Version 1.0a details