The Epic Hero Token is not only usable in the regular summons portal, buy also in the season events portal as mentioned by @EarlVerdant. Using them in those portals may net you legemdary heroes such as Master Lepus, Killhare and Sir Roostley from SpringVale, or Rana, Yunan and Roc from the SandEmpire, or Victor and a new red and green strong 5* heroes from Return to Morlovia starting this coming Monday, or Santa Claus, Mother North and Krampus from Santa’s Challenge this December. There are also good notable 4* heroes from those events too such as Buddy, Lady Woolerton, Jack O’Hare, etc.
But truth be told, that 20 EHTs of yours is not much. I have almost 4x that amount and there are several here in the forum with hundreds of them stocked in their inventory, hoarded for several months for the arrival of new heroes from the seasonal events.
At any rate, use them this Monday or on December. Hoard as many as you can as it is a free summon, FWIW.