The Collector's Intern

 is an NPC that replaces the Collector in Passages if the player is on Hell difficulty. They share all of the functionality for buying and upgrading items that the Collector does.

Dialogue
Upon first entering the Collector's room when 5 Boss Stem Cells are active:
 * "Hello there! I was waiting for you."
 * "Someone keeps leaving weird books all around the island."
 * "I want to try some of the... uh... stuff written there."
 * "But I need cells, the sort you’re carrying, for the experiments."
 * "Bring me some, and I will help you in exchange, would ya darling?"

Trivia

 * As mentioned in the patch notes and evident in the update banner, the Collector's Intern is of the same species as Guillain.