The Crusade is part of the Time Portal building and comprises of 9 different stages to complete on a daily basis.
Only level 30 heroes or higher can participate.
The health of heroes does not reset during a crusade, and any that die during a battle will be eliminated from continuing. You can however revive them using Life Orbs, at the cost of 100 diamonds.
The difficulty of it will scale depending on the power of your heroes.
Each stage will reward either Battle Coins or Hero Fragments.
Every 3 stages completed will reward a Chrono Star for the Time Portal building.