Activating this mod in the version 1.9.1 in an existing save that never had Rampant enabled before gives me the following error:
Error while running event RampantFixed::on_tick (ID 0)
__RampantFixed__/libs/BaseUtils.lua:81: attempt to index field 'evoToTierMapping' (a nil value)
stack traceback:
__RampantFixed__/libs/BaseUtils.lua:81: in function <__RampantFixed__/libs/BaseUtils.lua:74>
(...tail calls...)
__RampantFixed__/control.lua:1299: in function <__RampantFixed__/control.lua:1229>
I tried this before with a different back-up of the save file but with 1.9.0 and it worked back then just fine. But 1.9.1 just reproducibly crashes for me for that save.