It gives out Hard tokens and in the cash shop challengers tab it's listed between Forj Matriarch, Rekindled and Lich Lord (for me anyway, and unless I've been stupid, I should have all challengers unlocked).

Fixed, thank you :)

Great! It's still missing from the list of all opponents. Sorry, I'd add it myself, but I'm way too afraid I'll break something. Everytime I open the sheet it bombs me with suggestions on what it thinks should be edited, and those automatic edits are bound to screw everything up.

Not a problem, thanks for pointing it out and letting me know if you aren't sure! It's better for me to add something than to figure out a mistake

The auto-fill is quite annoying, I don't think that can be turned off :c

Added it, and feel free to let me know if I've missed anything else!