I like the HP bonuses on the human pretenders. To me, it says that you will no longer be forced to take death magic if you choose them (for Twiceborn). It still makes a lot of sense to do so, of course. But you arent really *forced* to do so, anymore.
If the Pretender in question can be affected by Twiceborn, it will work on her. This spell does not work for lifeless Pretenders, Undeads and various Demons.
On animate pretenders, sure - not undead or most immobiles. Additionally, becoming a wight mage is only a good thing for a handful of pretenders - the human mages being the most prominent example.
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Wormwood and wine, and the bitter taste of ashes.