Hearthpwn

This deck is very strong in upper ladder as it can beat out many control and combo decks by quickly filling up a nearly unclearable board and still play board control/survival against meta aggro decks. There are an insane amount of late-game cube combos, including some very heavy King Krush and cube damage. 

Mulligans definitely depend on matchups but for a general rule, always keep DS Rexar, keep egg/terrorscale, try to mulligan for keleseth, and stitched tracker is always a great tool to keep.

I added some tech cards like ooz and MC tech, but feel free to substitute these if you feel more comfortable with other options.