The Tower of Strife is a 150 floor tower which most likely resets on a 45 day cycle. You can climb the tower by fighting a 3 wave encounter at each floor. You will encounter a boss level every 30 levels. Each cycle players will select Chaos or Order when starting the tower. This decision locks you into that allegiance for the cycle so chose wisely.
Each gives a separate path and rewards for that cycle. Showcased rewards in videos include Order or Chaos summoning stones, gems, gold, energy potions, books. It appears that the summoning stones from the tower have an altered summoning pool based on that rotation to make i easier to get one of those heroes.
Information regarding the Tower are here from FATELESS:
https://www.youtube.com/watch?v=J7BbsJIW7pI