This was a Bad End failstate, Taker choose the wrong dialogue option. Instead of that Glorious Success, he is trapped as the very thing he hates. Really, when it comes to turning people furry, Lucifer was much more subtle in comparison, and succeeded far more.

Will Helltaker be taken by this ravenous beast? Or will Luci step in to protect her man and remain Top Bitch of the harem?

"Grand Master" too, I suppose that's in reference to the Templars that were burned at the stake for supposedly worshipping Baphomet.

Helltaker: Lucy?
Lucifer: Y-yes?
Helltaker: Take the girls, and RUN.
>Helltaker opens a previously always locked closet revealing a Praetor Suit
Helltaker: Unlike my brother I have some mercy. 10 seconds, I'd use them.