Cornerstone is the fourth and final Chapter in Act 5: Elder's War, and was released on December 15, 2017. Each Quest in this Chapter has a locked camera view, and its portals contain hints for their respective paths. The final boss is Ultron (Classic) 
.
It is preceded by 5.3: The Struggle and is succeeded by 6.1: Great Revival.
Description[]
NOW I CAN SEE THAT WE’RE FALLING APART
The Grandmaster’s grip on the Champions of The Contest has slipped, his focus spread thin across an increasingly chaotic realm. With a window of opportunity presented to them, those resisting The Grandmaster’s rule double down in their efforts to find the missing pieces of the Cornerstone that holds The Battlerealm together, but their increased activity forces him to focus his cruel attention upon them, and strike back with his most powerful Champions to date… Can you and The Resistance muster your remaining strength and allies to repair the Cornerstone and discover the cause of all this chaos? Will The Grandmaster and his Lieutenants counter your strength and stand in your way?
FROM THE WAY THAT IT USED TO BE…. YEAAAAH
While the final Chapter of Act 5 might have some new additions, The Grandmaster isn’t above dusting off some of his trickiest tools to test your toughness. A locked camera view will keep you on your toes, while Portals whose names contain hints at the path they lead to will make things even more interesting! New Buffs and Opponents will no doubt keep things unpredictable as well, so be sure to pay attention in each map so you’ll know what team to bring!
Quests[]
- 5-4-1 Contact (Punisher 2099
) - 5-4-2 Friends and Foes (Morningstar )
- 5-4-3 Calculations (Hela )
- 5-4-4 Do the Impossible (M.O.D.O.K. )
- 5-4-5 Break the Unbreakable (Mephisto )
- 5-4-6 Fight the Power (Ultron (Classic) )
Rewards[]
5,000x 5-Star Crystal Shards
18,000x Tier 2 Alpha Catalyst Fragments
1x Tier 4 Basic Catalyst- 60x Tier 4 Class Catalyst Fragment Crystal
- 1x Tier 4 Class Catalyst Crystal
10,000x 5-Star Crystal Shards
1x 5-Star Hero Crystal
1x 5-Star Awakening Gem Crystal
2x Tier 4 Class Catalyst Crystal