[Stub, Suggestion] Challenge event skins for regular heroes and avatars
Add Challenge event only skins for regular heroes. Not all heroes, but enough to make it worth keeping two copies of the reskinned hero, regular and event skin.
Event summons for Knights could summons a reskinned Rigard with an Avalon themed costume.
Pirates might summons a reskinned Marjana with an undead theme.
Guardians might summon a reskinned Wu Kong with a clockwork theme.
If you summon a reskinned hero during the challenge event, you get a free avatar based off the reskinned look to show off to your friends.