Cost/Benefit for Castle types

[NTJedi]

Ironhawk said:
I like this idea. It would be a great response to the madcastling conundrum.

BUT

If you were implement it (were that even possible in dom2) you would simply be waltzing straight into the "ghost rider's are overpowered" holy war, because this effectively removes the only cost-effective defense to it.

Ghost Riders is overpowered:
Lots of FAST longdead horsemen(speed is what's really huge)
The wraithlord leader(I've seen this fella win provinces in long battles even tho his horsemen died long ago.)
Only 5 DeathGems ! (most Patrolling groups with province defense won't survive a double casting)


Any of these suggestions for making the spell more balanced would be great:
1) Switch the wraithlord with a mummy
2) Increase the cost of gems from 5 to 8
3) Place a chance of failure or chance the spell hits some other random province