[llamabeast]

Yeah, you can change AOE, range, make it only affect undead, whatever. There is a huge amount of flexibility. But the effect would always be (for example) +4 strength. And you can't do entirely new effects - for example there is no spell to add Poison Spines to a unit, do you can't make a new spell to do it.

Technically you can only use #onebattlespell (automatic casting of spell at start of battle) for existing spells, but in practice we've got a very good workaround so it's not actually an issue.