I'm trying to get Snowbeast as a challenger in the Battledome, but I can't seem to find him. People say that you get him by refreshing at Advent Calendar. Is there any other place with a higher chance of finding him?

Just keep refreshing there. You will eventually get it.

There were reports that you can also get the snowbeast challenger while playing cliffhanger...

The way many claim to work (worked to me) was to refresh at AC till an random/winter/anywho event, then change to cliffhanger, do the same there and back to AC and continue this till you get him.

um i thought you got him from the the snow wagger event i thought thats how i pulled it off....

Just got snow beast challenge message!! :D only took about 7 refreshes at the advent calendar....i guess adding 10 lutari talisman beads helped :O