Ok, so we don't know how Margaret's death curse works. Maybe it's only attached to Harry and Thomas. It's not fueled by her bloodline. Just the two of them. It stopped being fueled by Harry when he died. Any of the times. Now that Thomas is imprisoned, he's not fueling it anymore. Lord Raith is now free.
Alternatively, it was only ever tied to Harry, and Lord Raith has been free and secretly building up his strength since Changes.
The interesting thing is the connection between Raith and the Outsiders.
- Raith's protection spell is (presumed to be) provided by Outside.
- His disciple Madge summoned Behind.
- His nephew wasn't just unknowingly working for greater powers, he was confirmed as possessed by an Outsider (Before, via loose WoJ)
li] Beside possessed Justine, which gave him access to Raith.[/li]
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That dude is neck deep in all of it. So if it's Maggie's curse ending, or Beside helping him via Justine, or some other method, He's definitely not done, story-wise.
(There was a time I thought Raith was possessed by Beside, who was doubling the protection to spell to protect his anchor host in reality, but that would all but require that he be able to have multiple hosts)