Spell:Shadowcloak

Birthright spell

Quick at-a-glance summary of what the spell does.
The wizard appears to be a native of the Shadow World to all denizens of the Shadow World and increases their Seeming score for the duration of the spell. Source: Homebrew User:AndrewTall

A shadow cloak is not, in fact, a black cloth of woven fabric that swishes coolly in the absence of wind, buffeted only by great deeds and aura's of doom. Sorry.
A shadow cloak is simply an aura that overlays that of the recipient, to the otherworldly sense of the denizens of the Shadow World the recipient feels like 'one of them' - undead consider the recipient to be undead, Seelie sense the recipient as more than merely mortal, etc. This has the effect of making most minor threats of the shadow world simply ignore the recipient.
The cloak has a second aspect which is only accessible if the recipient makes a knowledge:Shadow World check at DC 15. If the check is passed then the cloak adds 1 to the seeming score of the recipient for every 2 caster levels of the person who cast the Shadowcloak.

Although the spell makes the recipient 'fit in', this does not make every denizen of the Shadow World friendly - far from, most will simply ignore the recipient. Sidhe however will appear as (un)seelie, legend says that in fact a sidhe who casts this spell repeatedly may in fact become a seelie, however this is surely just rumor.

As few spell-casters willingly risk entering the Shadow World this an unsurprisingly rare spell. The halflings probably have the most knowledge of the spell, followed by the Sidhe. Of all the human tribes the Anuireans were most interested in the Shadow World for its military applications (of which Michael Roele's ghost legions are but the most famous example). The Khinasi consider the ever-shifting seeming to be inherently irrational and built on lies and illusion which together with their scorn for necromancy leads them to have little knowledge of the Shadow world, the Brecht simply see no profit in the realm.

No change needed.