blessed be thy emperor wrote:How would one go about creating rules for
apoc?
I'm considering building a large tank or titan for a sisters of battle force (I know the titan doesnt make sense but let me have my fun

)
It actually makes a lot of sense for a Apocalypse-sized Sisters of Battle forces to make use of titans and super-heavies. The Witchhunters Codex allows you to induct
IG units, and even if it didn't, Apocalypse allows you to mix units from different army books. And honestly, some of the Imperial superheavies are pretty appropriate for an SOB army. The Stormlord in particular looks like a good fit, what with the mega bolter, and the heavy flamers, and the fiery death.
If you want something unique, I'd start with an existing super-heavy, swap some sort of super-melta into the turret, and try to come up with a fair price. If you show what you're basing it on, I suspect it won't cause many problems, since mega-battles tend to be pretty sloppy about things like exact point costs.