Nybeth?
Denam chases Nybeth into the Palace of the Dead and encounters him several times. After Denam delivers a mortal wound, Nybeth uses a Ring of the Dead to transform himself into a lich and continue further into the Palace.
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Not really fan of all these in-game bonus items coming with albums, books and statues - one FC-member is trying to get all music rolls, and with two of them hidden behind "Duality" album, he'd need to buy it.