Another idea - why not have him have to life half his life as prey, and only the other as hunter?
If you want him to be recurring, you might consider loosing him on the demiplane at large - maybe he's a ghost/incorporeal undead. So, he brings with each possession, say, a new body, but all of his hunter's knowledge. And then he uises this body to hunt some worthy foe. It a wierd way, he may believe himself to be some instrument of divine vengeance, able to strike at the powerful and canny on behalf of the powerless? (of course, that fact that the bodies are often destoryed or abandonned once the quest is done?...)
Or, a form of Ancient Dead which just regenerates when killed...
There are a lot of things you could do. If you want a GREAT one-use adv, I might go with the island. If you want something long-term, I would let him roam.
Let's say the PCs come after him, confront him and he escpaes? Then the hunter becomes the hunted... or does he? Maybe he evades the PCs, sets them on a false track...l only to come up behind them and start trailing them while they "hunt" a non-existant "prey just around the corner"? Once they finally reaize what's happened, he pounces, kills ONE of the PCs (or maybe a fellow NPC) then dissapears. he leaves them alone for a whilem, so they think he's gone and they're looking for his cent... only to realize he's behind them again... repeat until the PCs are living in constant fear!
the best part about this approach: you have the 1st attack at low-level PCs. So, they know the guy is out there, being to hunt him, then the scenario plays out. When they finally conrner him, they CAN"T KILL HIM! he's too tough! So they run away... a and are basicaly forced to become monster hunters to grow in power to fight him!... all the while watching over their shoulders...
(One of the ideas I don't like the hunter domain lord on an island - how hard is it to kill a creature in a cage? That's essentially what that is if the characters are trapped in his realm... I guess that could be his curse - maybe he can't OPEN the borders to allow the characters to escape, to make it a REAL challenge?... So the border is always open one way, and always closed the other?... Just an idea...)
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