IIRC, the crowns keep several powers even if the Forge is destroyed.
The power to 'feel the realm and it's borders' ( and anything associated to it ) is lost, but all the other powers are left.
In the campaigns I played ( as a player and as a DM ) even if the forge was not destroyed, it was disabled, so the power of the crown failed too.
In one case Kier was defeated in a battle, but managed to escape and started to do some skirmishing maneuvers around Helissa, in another case, he won and drove Lorgali's forces back into Xa'ar, but he still had to wrestle internally with the remnants of the Yarthraak priests and a few people that would have prefered to be under Lorgalis rule.