The Slaad

The Slaad are an intelligent race of aberrations who are tied closely to the Plane of Limbo. They are by nature chaotic, and breed by impregnating humanoids with their eggs, that hatch out of these victims. Sometimes a they will use a disease called Chaos Phage to forcibly convert a humanoid into another Slaad. They seem to be a natural feature of Limbo, keeping the souls in this Plane under control and tracking down escapees, especially on the Material Plane.
They can be summoned to the Material Plane my mortal mages who find their chaotic energy hard to control. A few escape and live in secluded regions away from others.
Each of the Slaad are can be traced back to what is known as the Spawning Stone, placed in Limbo by Primus, a god of order. The stone, had small parts break off, when infused with enough chaotic energy. Originally the stone was to bring order to Limbo, but couldn't fully function because of the sheer chaos of the plane. When these broke off they changed colour and from each one sprung the Slaadi. The only slight difference was the death slaadi, as the stone they originally sprang from was infused with energy from the Negative Plane, and caused these to warp. After this happened, the slaadi naturally developed their own reproductive cycles.
They took over the running of Limbo on a daily basis, and when souls arrive in Limbo, they usually sort them the best they can. This is as haphazard as can be as the Slaadi are not known for sticking to any exact routines or order in the first place. All they know is that they have to shepherd these souls around their domain.
Initially when the species came about, the Spawning Stone placed a part of itself into the brains of the first Slaadi. These are known as Slaad Control Gems. They are the size of a human baby's fist and the same colour as the Slaad they are found in. This stone is not found in any slaad born by other means.