If Chakax is in a unit of temple guard with a slann they gain unbreakable(ultimate body guard). However i want a scar-vet in there as well. Can it just not happen? what happens if I have the scar-vet and a slann in the unit and then chakax joins. Does the scarvet get kicked out? can Chakax just not join?
Hmm, good question. The LM book says... The BRB says... Keep in mind that Chakax himself is not Unbreakable on his own. Only when he joins the unit, every MODEL gains the rule. The word model is key here. That means that the Scar-Veteran would gain Unbreakable since he would already be a part of that unit. Now if the Scar-Vet was not deployed with the unit initially, he cannot join unless Chakax were to leave. (or die... ) EDIT: Same thing with Lord Kroak. A Scar-Vet can be deployed with the unit, but cannot join unless Kroak were to leave first.
As a Skaven player too - I can attest that a Screaming Bell unit is unbreakable, you can add whatever characters you want to when it's deployed however - NO ONE CAN LEAVE OR JOIN THE UNIT AFTER DEPLOYMENT. So don't be trying to charge your scar vet out again.
There wouldn't, in this case, be anything preventing your Scar-Vet from leaving the unit. The reason other characters cannot leave the Bell/Furnace units are because of the rules for these warmachines... (both the 'Altar of the Horned Rat' and 'Icon of the Horned Rat' rules on pages 42 and 48 end with "neither can voluntarily leave the [Bell/Furnace]"). So although you can deploy the Vet in the Slann+Chakax unit, same Vet can leave the unit at any point but will thereafter be unable to join the unit...