Complex sentence: The vulnerable minds of the young races allowed these creatures to enter the galaxy in ever increasing numbers, the most proficient of these were the Enslavers (not to be confused with true Daemons).
Split into simpler sentences: The vulnerable minds of the young races allowed these creatures to enter the galaxy in ever increasing numbers. The most proficient of these warp-creatures were the Enslavers (not to be confused with true Daemons).