"Some men are alive simply because it is against the law to kill them."
NOTE: These have not yet been reviewed for Wraith20 update, Wraith20 416-417 seems to be the equivalent
More info: Wraith20 page 285
There seems to be some misunderstanding of who/what is exactly immune to various forms of supernatural innate powers. The following is a list of what's what for the races that have such:
The Fog - Some are not affected by the Fog: Children, animals, some gifted adults, and certain of the other supernatural denizens of the World of Darkness. (Wraith20 page 284)
Deathsight (Wraith20 126) can detect that someone isn't aging (e.g. Unaging merit, demon with non-empty Faith pool), but doesn't tell the wraith why.
Lifesight (Wraith20 126) uses same result chart as Auspex 2 (Aura Perception, VtM 150), but base diff 5 instead of 8.
PCs can choose to spend Shadow XP on their Shadow (Wraith20 302-303). This will be tracked in +notes.
"...few Garou dare the Dark Umbra. ... The restless dead that haunt the living - and us - are just the tip of the iceberg. Ghosts are like cockroaches. For every one you see, there's at least a dozen more you don't. That many ghosts don't get together without someone trying to be in charge. So you get entire kingdoms of dead people. Kingdoms with armies. Don't think just because you're some big bad Garou you can walk in and start throwing your weight around. They'll dog pile your ass and beat you down." (Silent Striders 51-52)
"Most mages never venture into the Low Umbra, and few of those who do return to tell about it." (Beyond the Barriers: The Book of Worlds 12)
"Finding one's way through anything but the Low Penumbra is nigh impossible at best. In the unlikely event a living mage finds herself in the Afterworlds, it is best remembered that those who journey down among the dead in the time after the Reckoning are almost always fated to remain there." (The Infinite Tapestry 26)
In short, a non-wraith entering the Shadowlands is a Big Deal. Surviving it is possible, but anyone claiming it's easy is simply wrong.
Powers targeting a specific wraith (e.g. Sepulchre Path 2) do so normally. Powers that merely target a type of wraith, only target a PC if the wraith and summoner OOCly agree to let it happen.
'Killing' a wraith (Corpus reduced to zero) with aggravated damage triggers a Destruction Harrowing. (Wraith20 244, 293; takes precedence over other game lines)
Mages: Spirit 3 Entropy 3 attacks do aggravated damage. Otherwise, the mage can only attack the wraith if they're on the same plane of existence. (MtA 282)
Sorcerers: Summoning/Binding/Warding 'ghosts' refers to wraiths/spectres.
Warding using Willpower (WtO 287-288):