To dance with the lightning in the raging sky, to dive into the fire-river and follow it all the way to the heart of a planet, to taste colour, to see sound, to feel light... the gift of Esh to the Ka'am is the gift of freedom, change and experience. May we always cherish it.
A Sii's physical form is that of a small, pink slug-like creature. In this state, though still possessed of prodigious mental faculties, a Sii is not able to achieve much physically. This limitation is overcome by merging with a host form: the slug-like body of the Sii enters the cranial cavity of its host and wraps itself around the cerebral cortex; tendrils are extended and contact points established. The Sii is then able to manipulate its host at will, though exerting control requires continuous and unceasing effort. Thus merged, the Sii attains a true and complete existence, for we are symbiotes. The host forms available to a Sii is very much a foundation of his combat strength.
To this end, we have harvested the DNA material of dozens of alien species as our Great War raged across the galaxy. With our technology, we are able to recreate host forms at will, if the resources are available. This comprises our biological arsenal and we have brought these host forms with us to our new home.
It should also be noted that these forms are non-sentient and cannot function without a Sii in control, more akin to biological mobile suits constituted from DNA and modified to be so by our formsmiths. There is no question of a being trapped in its own body, powerless to exercise control. This is not because the warring factions of the Ka'lee are noted for their altruism or advanced moral code - pragmatically, the upkeep of unresisting forms is much lower.
Host forms are carefully tended to by our formsmiths. It is their highest responsibility to ensure the suitability of a form for merging by tweaking its DNA structure, and to maintain a constant and ready supply of fit host bodies via cloning and cryogenic storage. Sometimes, these biological wizards may even concoct new form types - these are known as rare or exotic forms and will be denoted with an asterisk (*). Moreoever, great deeds in service of the Sii can be rewarded with access to even more peculiar and wondrous forms. These deed forms are denoted with a hex (#).