I haven´t seen it mentioned anywhere, and I´d miss it too, if I didn´t casually check the in-game shop, so I thought I might post about it. If it was, I´m sorry. They´re the 4 Hero skins from the Lunar New Year event from 2 years ago and you can buy the skins for 1000 gold, except for Valeera, she is for 1500 with cardback.