The linking characteristics of the type of monster(s) found outside of Eniherjar will be consistent with that of the types found within.
The enemies come in three waves, with the first and second wave each featuring 1 type of the below enemies (excluding enemies spawned from bosses), and the third wave featuring 1-2 types of the below enemies plus a boss.
Huginn, Muninn, Heithrun or Saehrimnir will not be immediately seen. They will pop as you progress through the chamber's monsters. Muninn and Saehrimnir will leave behind a message stating "the chamber's stagnant aura has somewhat cleared" if defeated or left to depop respectively.
Huginn will leave behind an Armoury Crate containing various consumable items upon defeat.
Muninn will weaken the enemies upon defeat. A message stating "the creatures lurking in the shadows have calmed" will be received.
Heithrun is the rarest of the four and will double the items in treasure chest after defeating boss.
Saehrimnir will strengthen the enemies if left to despawn. A message stating "the creatures lurking in the shadows have become restless" will be received.