I'm not certain if this classifies as a bug or simply a limitation in how NPCs work.
When I set up a Citizens NPC with the Magic trait and set the spell to fury, the spell does initiate casting and the first effects do play, however no targets seem to be picked from there.

The spell simply vanishes instantly and nothing further happens.

What could be the cause behind that and is there any way I can modify the fury spell to work or create a spell similar to fury that does target enemies when cast from an NPC? If this is a bug or limitation on NPCs end that can be fixed, it stands to reason that similarly functioning spells will also benefit from it.

I think I found the cause, though it is a bit awkward, it seems the spell needs to specify that target_game_modes includes creative as this seems to be the gamemode the npc is standard in and AreaOfEffect attempts to target the npc itself.
Moreover, the fury spell requires the npc to not auto-target the player, for which there was already an option available, I will have to get my own plugin to override that paramater on demand too.