Exchange Vitality

You gain this spell on a roll of 17 or 67 on the Forbidden Spells Table.

You exchange your current hit points with another creature's current hit points.  Any hit points that would go above your maximum hit points instead become temporary hit points with a maximum equal to your hit point maximum.  You may use this ability at any amount of hit points, or as a reaction if you are within 10 of your maximum.

In addition to the usual Forbidden Spell penalties you also lose a number of hit points off your hit point maximum equal to 1/2 the temporary hit points you gained or 10, whichever is more.