This is nice for Campaign if you do campaign battles. The effect is only active if you have tags equipped. It's also a good substitute for an empowering mantle +1 as any job can equip it.
Tested today, If you have campaign regen or refresh the extra MP added from the latent doesn't seem to stack.
Example : if you have 1000MP base and equip the cape it'll add +15 MP totaling 1015mp. If you get equip tags you'll be upgraded another 15 MP and get a 5% MP bonus upgrading MP to 1081.
Unfortunately, the allied Sigil auto-refresh effect is a latent percentage based on how many areas your nation has under control. What I'm getting at using the above example. Sixty-six MP of the bonus added from the items latent seems to be ignored by the sigil refresh effect.
I have yet to find any hidden effects.
Edited, Jan 5th 2009 4:32am by Saricks