Added some magic events

Serpent staff projectiles now cause a debuff that makes mobs
non-hostile, using a custom potion effect (with a dynamic id for
cross-mod respect, hopefully)

Also the twilight cloak now makes you "actually" invisible. Mobs will
not target you while it is active.
Disrupt Existing Hostility

for twilight cloak and serpent staff debuff. Now anything that already
had a target will have their target disrupted by their respective
effects.