So what will happen is that
Urza will be resurrected, just like the sundering in D&D. He then ports every major player in the multiverse to compete in
Urza's Unstable Battle Royal.
The Gatewatch have to fight in
arena matches to the death. (Just because)
Jace loses his eyes after having them gouged out by Kiora's trident. However, he manages to use his telepath powers to make Kiora beat herself to death with her own tentacles.
Gideon meanwhile loses his arm after Nahiri cleaves it off with her lithomancer blade, but his hand tents/surals w/e manage to
sunder her blade with her, just as she thinks he's defeated.
Tezzeret has his etherium arm torn off by Garruk, which Garruk uses to beat him to death with. (It is later given to Gideon, grafted in place of his missing arms).
Khan pulls off Nissa's limbs when she tries to swallow him in a
sinkhole. (Because that's what golems do, right?)
Liliana uses
the chain veil on Sorin, turning him into her corpse puppet, which she makes dance to entertain children on weekends.
Meanwhile, Chandra lights up the
arena with some fancy pyromantic displays, inadvertently blinding Vraska in the process.
Seeing her advantage Chandra immolates Vraska's hair snakes offering it to the spectators as street food.