Chaos Infused is a trait or property of a creature, area, or item. It comes about from contact with very strong entropic energy from Chaos, artifacts of chaos, the Decomposition String, or very old and powerful chaotic creatures. The effects of chaos infusion are random in what they do and in their strength. Some creatures from Chaos have the ability to chaos infuse areas, and a very few can change others. In the Hoof Front, Tiamat battled an ancient demon which infused her with chaotic evil energies. Tiamat was able to shake-off the chaos, but not before she was warped into a monstrous dragon with multiple heads.
The chaos behemoth, like those of the Horde of Chaos, is a monster that infuses areas with chaotic energies. In the Chaos War, chaos behemoths were used to warp the areas they passed through. A dozen of them were used to turn the ruins of cities into chaotic places with floating structures, rubble, and things shifted about in a haphazard pattern. These areas became known as chaos ruins.
Chaos rocs are birds of prey that chaos infuse their victims by way of their claws. The effect is not as bad as the chaos behemoths, but it can be deadly. Healing applied to an infected chaos wound may either heal or damage the target, the chance is equal for either outcome. In the legend Elephant Reverene, a great hero dies from the wounds he suffered from a chaos roc.
Some primordials were masters of manipulating the energies of Chaos. One example of this is Sarseg. This being was a weave spider of the Web of Magic. It was somehow overcome and then infused with chaos. It lost its bond to the Web of Magic and became a free-willed, chaotic weave spider. Blibdoolpoolp is another primordial that used entropic energies to transform divine creations of others into a new race that looks very much like her (c.f. kuo-toa).
Another thing that can chaos infuse even those of near-divine power is the Decomposition String. In the Creation War, Tarâk and the Slaad Hexos were forever changed when they extracted warp matter from the Decomposition String.
Yagolorn is one area of the realm that is infused with the chaotic energies of Chaos. At the heart of this wasteland is the petrified arm of a long dead primordial. This area is believed to have become chaos infused when this primordial was slain in the Creation War.
The landscape of Flux is also chaos infused. It was made this way when chaos cultists of Neld-Rac opened up a inter-system gateway to Limbo. When the Chaos Maelstrom flooded through this gateway it forever changed the lands and has hung over the area ever since.