Soul of the Sanctum Keeper - limesplatus/Ultris GitHub Wiki
<- Home
The Soul of the Sanctum Keeper is a custom mob in Ultris that appears after defeating the Sanctum Keeper. It echoes the sounds of the Sanctum Keeper, and unlike other souls in the Sanctum, it does not despawn after finding. The Soul of the Sanctum Keeper is immune to all damage and cannot be killed by anything, except for the void.
Holding an emerald in your mainhand or offhand will make the Soul follow you around. When near you, it'll apply the resistance 2 effect. Keep in mind other nearby players holding emeralds will also attract it.
If you fly with an elytra whilst the Soul is following you, the Soul of the Sanctum Keeper will speed up to match the speed of your flying.
Unlike most minions/pets, the Soul of the Sanctum Keeper will not teleport back to you after a death.