I believe they are added automatically.
If you do win them, contact support, and they'd be happy to remove them for you.
Correct, there are no chances to get challenges, those are completed already.
on November 25, 2014 4:08 AM
Grinding Gear Games
We are investigating an issue with the Haku crafting benches after the league transfer.
The crafting benches of other masters can be attained by talking the the appropriate master in your hideout.