Battle-forged Heroes

[AirHorse]

I'm just in the process of attempting to paint up some marines ive got as exorcists and while toying with some prospective lists I was thinkng about using an exorcists version of Cato Sicarius.

Having read through his battle-forged heroes ability I realised it wasn't totaly obvious exactly when you are supposed to decide which of the special abilities you give to your chosen tactical squad. It talks about it having no additional cost, so on the basis that it might have had a cost I guess it would mean you have to declare this on your list, but its not that clear.

Thought I would ask for a hand clarifying this just incase I lose some flexibility that I might enjoy if you dont have to declare this on your list. Thanks in advance for any help :)

[Gotthammer]

When I've used Sicarius I've declared it on the list, keeping it the same throughout for a whole tourney. I'm not basing this on anything really, just seemed the easiest way to avoid anyone getting uppity about it.