For about 15 days or more (santa 1 month), these events have a calendar of daily offers.
Epic tokens can be used to summon seasonal heroes.
There are minimum 20 levels (2 modes : normal and advanced) and no rankings
I guess somewhere along the way (next year), SGG might also include the Jack O’ Hare avatar as the reward for completing stage 10 in the Advanced Tier of Springvale (as they did with Valeria in the Return to Morlovia this year). Problem is, next time Springvale comes along, they are probably going to have to implement a system to check to see if the player already have the Squire Wabbit and Master Lepus Avatars and provide something else as alternative rewards since repeated avatars aren’t really useful.