Riftwalkers must periodically wander the rift world to ensnare entities, either because they want a new entity type, or because they need to feed an existing entity. This skill reduces the spellpoint loss of being in the rift world, enabling longer visits. If you are spending large periods of time using the ‘seek’ command in the rifts, this skill may prove valuable.
I don’t have any information on if this skill helps while inside the rift boss worlds.
The in game help reads:
Skill duration: random. Type of skill : automatic skill (arcane skill). Affecting stats: None. It uses no endurance points. This skill will allow an explorer of a rift world to resist its inhospitable environment for a longer period of time.