Conversation so far:
What was the Hellfire Club?
The Hellfire Club is a fictional society appearing in American comic books published by Marvel Comics.
Why was Sage sent to spy on the Hellfire Club?
Sage is sent to spy on the Hellfire Club as Tessa, and to keep watch on Sebastian Shaw.

Question: Why was he recruiting them?
Self-contained rewrite: Why was Charles Xavier recruiting X-Men?