Spell:Blood Drain

Birthright spell

The caster drains bloodline points from the target permanently. Source: BoM.

This spell, most often used on a helpless captive, allows the caster to drain bloodline strength from the victim and use them to increase their own bloodline.
The victim gets a will save (with their bloodline score modifier added as well) vs DC 5 + effective caster level to avoid the effects of the spell. A save by more than 10 reverses the flow of bloodline strength...
The spell affects 2d8 points of bloodline strength, these are effectively released as a regency storm, albeit with the casting scion inevitably in physical contact with the victim.
As with any bloodline transfer there is a risk of bloodline corruption in the spell, for corruption purposes multiple castings of the spell within a 2 week period are cumulative, so if 5 bloodline strength points were drained each day for 5 days, the corruption check would be made on 5 points on day 1, 10 points on day 2, and so on up to 25 points on day 5.
A faint mystical link exists between the caster and victim for 2 weeks after the casting, if within this time period the victim receives a dispel magic, or similar spell, which is sufficiently powerful to dispel the Blood Drain, then some of the stolen bloodline strength may be recovered (DM's discretion based on time delay, alignment harmony with bloodline, etc).

While scion's tend to see usurpation, bloodtheft and the like as inherently evil, often equating it with cannibalism, most nobles are extremely pragmatic. As such were this spell to become widely known of, it would attract some approbation, but not as much as outright bloodtheft.

The only wizard known to have cast this spell is the dreaded Magian of Pipyret although it is rumored to be known by the sidhe.

The CT of the spell per BoM is 4.