I have a level 9 Gnoll Warlock who is Best friends and taught by Guldan (long story). However, he kept believing in the spirits. Immortality has not triggered. The wiki tells me nothing. He technically doesn't meet the minimum requirements anyway, with 9 and 9 for intrigue and learning (instead of 8 and 12); I just was willing to play him until he leveled up; this was at age 60. Fel corruption is zero.

How do I trigger immortality? Am I meant to absorb crystals until I become fully corrupted? Or what?