Elan
Factotum/Telflammar Shadowlord (possible Soul Eater dip, hence Elan.)
The recipient may enter an area of shadow as a standard action and emerge immediately from another such area that is no more than 100 feet away. This power is a supernatural ability that the recipient can invoke at will. Each time she invokes this power, she suffers 2 points of temporary Constitution damage and a loss of 2d4 hit points. The ritual user may also hide within the shadowstuff, rather than emerging, but the cost for doing so is even higher: For every round the recipient does not emerge from the area of shadow, she suffers 4 points of temporary Constitution damage and a loss of 3d4 hit points. Should the recipient’s hit points be reduced to 0 or less, or should her Constitution score drop below 1, her body is claimed by the shadowstuff and remains trapped within forever.
The ritual requires a piece of jet worth 500 gp or more and drains
2,000 XP from the recipient.
Cunning Surge->Shadow Walk->Shadow Pounce->Repeat.
I need to negate the CON damage, but the XP burn from this ritual already hurts, So Necropolitan is probably a bad idea.
Strongheart vest looks like it needs a very high character level, so that's out for now.
Starting at level 5, needs to be usable as early as possible.
EDIT: All books available, Injury Variant is in use.