Rat, Vapour (CR 2)

Tiny Magical Beast
Alignment: Neutral
Initiative: +3 (Dex); Senses: scent

AC: 15 (+3 Dex, +2 size), touch 15, flat-footed 12
Hit Dice: 2d10 (11 hp)
Fort +3, Ref +6, Will +4
Speed: 30 ft., swim 15 ft., burrow 5 ft.
Space: 5 ft./5 ft.
Base Attack +2; Grapple -10
Attack: Bite +7
Full Attack: Bite +7
Damage: Bite 1d4-4
Special Attacks/Actions: Stinking cloud
Abilities: Str 2, Dex 17, Con 10, Int 4, Wis 12, Cha 2
Special Qualities: gaseous form
Feats: Weapon Finesse (bite)
Skills: Balance +5, Climb -2, Hide +6, and Move Silently +5
Advancement: -
Climate/Terrain: Any land and cloud islands
Organization: Pack (2-16)
Treasure/Possessions: None

Source: Converted

As with other rats, vapour rats attack with a vicious bite.

Stinking cloud (Ex): Whenever a vapour rat is killed, its body gently explodes to form a gaseous release equivalent to a small (1d4+4 ft. radius) stinking cloud. The cloud dissipates after 1d4 rounds.

Gaseous form (Ex): Vapour rats can alter the substance of their bodies, effectively assuming a gaseous form. In this state, they appear to be wisps of cloud or similar vapour. In this form, they can only be affected by attacks that would destroy or dissipate their cloudstuff. Such attacks include very hot or magical fire, lightning, exceptionally strong winds, etc. If threatened, vapour rats will assume gaseous form in an attempt to escape.