This is a bug that has been in Patch 7 and unfortunately is also present in Patch 8.

If Lump The Enlightened is convinced to work for the main character and gives [Lump's Horn] to the player, this triggers a bug with the 3 ogres which causes them to instantly de-spawn mid-combat whenever they become hostile towards the player.

Example:

  • Player convinces the ogres to work for them and receives the horn
  • Player uses the horn to summon them
  • The ogres spawn in and begin a conversation (if nobody is around or after everyone is dead)
  • Choosing not to honor the deal, failing a skill check or directly attacking them turns them hostile and initiates combat
  • The combat starts and the ogres de-spawn one by one mid-combat after a couple of turns

This is a bug, as they shouldn't be de-spawning mid-combat.

Right now the only way to avoid this bug with the intent of killing them, is to summon them against another enemy and kill them during combat while they're still friendly, as they won't de-spawn as long as they're friendly and in combat.