I also haven't been able to use the clan worldspell in my latest game. Worldspells are enabled, there are no world spells active that block spellcasting, and I've made tried using it all the way through the game with no luck(I have pretty much all techs now).
can you use normal spells? if not:
i had a similar problem once and it was releted to a c++ bug (i think i used a buged version of "Saila, the Everchanging" module)
do you have PythonExceptions enabled?
edit:
found the thread - if you are using the Everchanging module v0.2 use this quick fix ( urlremoved/rife/forum/viewtopic.php?p=1492#p1492 )
The clan have a leader without barb trait? You absolutely must have peace in order to use that worldspell.
Yeah, I never play with unrestricted leaders, for that very reason.
Typo. Should be cf, for custom functions.