Chaos Elemental (3.5e Monster)

''This creature looks like a haze of amorphous matter, swirling around with no distinguisheable pattern. It is generally shapeless, and its everchanging body is invested with the nature of chaos, making it highly unpredictable''

When summoned to the Material Plane, an chaos elemental bubbles into view as if boiling into existence. Summoning an chaos elemental gives the summoning spell the Chaos descriptor.

Chaos Elementals are extremely vocal, but it's uncertain if the continuous noise they make, which ranges from gentle breezes and whispers to roars and jet engines, is an actual language. In any case, they understand Common.

Combat
A chaos elemental moves quickly, and strikes unpredictably. Larger chaos elementals slide about through the weave, creating a self-concealment effect, and the number of attacks that a chaos elemental can make is variable.

 Entropy (Su):  A chaos elemental's unpredictability grows with its age category. Any chaos elemental has an entropy score (ranging from 5 to 50 %, dependant on age category). This percentage applies to a self-concealment miss chance. Furthermore, on a full attack action a chaos elemental has a chance equal to his entropy percentage of gaining additional attacks over his usual maximum. After the chaos elemental finished its attacks for the round, roll a d%. At a successful check against the chaos elemental's entropy percentage, it gains another attack at its full attack bonus that round. This d% rolling is repeated until the first entropy check failure. Entropy does not stack with other concealment effects, such as blur, displacement and invisibility.