Challenge Mode Rewards

Elemental Crescent
Crystal-Shot Longrifle
Soul Eater
Tesseract Timepiece
Cloudsong Glaive
Face of the Guardian
Arcana Shard Spire
Staff of Infinite Knowledge
Shifting Felblade
Greatsword of the Inferno
Bloodmaw Gargoyle
Living Longbow
Dimension-Ripper Staff
Claws of Creation
Furnace of the Great Machine
Challengers War Yeti

Proving Grounds Rewards

Proving Grounds: Endless Damage
Proving Grounds: Endless Healer
Proving Grounds: Endless Tank