Eternus summons alternate evil party members. Eternus summons evil timeline versions of players that attempt to steal essence. If they reach their target, they cast Stolen Essence, reducing maximum health, damage done and healing done by -6% for 30 sec.
The unstable copies are constantly Unravelling, suffering 5% maximum health as Arcane damage every 1 sec sec.
Upon death, they instead cast Merged Essence and grant their target increased maximum health, damage done and healing done by 30% for 20 sec.