When a yellow Slaadi Licks a dead humanoid or beast it's necromatic saliva it revives and transforms the corpse into either a red or blue Slaadi depending on the temperature of the corpse (< 0 degrees C: blue, > 0 degrees C red).

The Spawning Stone. Long ago, Primus, overlord of the modrons, created a gigantic, geometrically complex stone imbued with the power of law. He then cast it adrift in Limbo, believing that the stone would bring order to the chaos of that plane and halt the spread of chaos to other planes. As the stone’s power grew, it became possible for creatures with ordered minds, such as modrons and githzerai, to create enclaves in Limbo. However, Primus’s creation had an unforeseen side effect: the chaotic energy absorbed by the stone spawned the horrors that came to be known as slaadi. Sages refer to Primus’s massive creation as the Spawning Stone for this reason.

The slaadi wiped out every last modron enclave in Limbo. As creatures of utter chaos, slaadi loathe modrons and attack them on sight. Nonetheless, Primus stands by his creation and either doesn’t perceive the slaadi as threats or chooses to ignore them.

Birth and Transformation. Slaadi have horrific cycles of reproduction. Slaadi reproduce either by implanting humanoid hosts with eggs, by infecting them with a transformative disease called chaos phage, or transforming dead humanoids or beast through there necromatic lick. Each color of slaad reproduces or transforms in a different way, with red slaadi spawning blue and green slaadi, yellow slaadi spawning red and blue, and blue slaadi spawning red, yellow and green. Each green slaad undergoes a lifelong cycle of transformation into the more powerful gray and death slaadi. With each transformation, the slaad retains its memories.

Shapechangers. Some slaadi can transform into the humanoid creatures from which they were originally spawned. These slaadi return to the Material Plane to sow discord in the guise of their former selves.