To whom it may concern,
Greetings! I would like to address my dilemma on why my Pets did not gain experience points after Black Spirit Mode in Elion nor Hadum. Are there changes?

Pets gain experience when they pick up loot chests that drop from enemies. In hadum these chests only drop once ever 120 seconds, and if you're using 3 pets then they each take a turn picking up that single chest. The experience is very little and even more so if you're going to be in black spirit mode while in hadum. Theoretically, the fastest way would be to hunt monsters in elion's realm that are close enough to your CP or else they wont drop anything. If black spirit mode doesn't give any pet exp while in elion's realm then yes that would be a bug i presume.