Rules Question - Possession

[chaoschild]

The summoning is successful – maybe. The nearest enemy model and the grand warlock must both make Will checks. If the grand warlock rolls a higher total, the enemy model has become possessed! He replaces three of his characteristics with those of the entity and comes under the control of the demonic cabal player. At the end of the game, he will automatically be counted as a casualty.

Does the victim of a possession attempt have to be alive to begin with? There's nothing in the rules to say that he does, but it seems downright odd for a robot, a zombie, one of the Dark Judges or even another demon to become possessed.

I know at the last tournament at Mongoose, people were playing it so that robots couldn't be possessed but I can't find any justification for that in the rules.

 

[Fattdex]

 

[Surtur]

Can you please explain me what is the context