Re: How do you want Xykon fail
I don't think Xykon has the right mentality to suffer a complete villianous breakdown; after all, we saw it come pretty close to what you are describing back in Azure city, and all we really got was a "we gave it our best shot, so much for that".
And Xykon got seriously angry at V and O-Chul when they broke in/out of his tower, but remains focused as ever.
Even if every gate is destroyed and/or kept out of his hands, what's 20 years down the tube to an immortal lich?
As satisfying as it might be, I think the best we're going to get is perhaps an "Oh [poop]!" moment with Xykon reduced to nothing but a skull as his phylactory is smashed.
"A man is known by the company he organizes." -Ambrose Bierce
Homebrew Extended Signature!
Progress in my Core rebalance project: 8 of 11 classes complete
Druid, Fighter, Cleric, Rogue, Ranger, Wizard, Sorcerer, & Monk
Magic Fix: rules complete; spell rewrites paused for playtesting
Non-core stuff I want to take a crack at rewriting: Healer, Warlock, Ninja, Samurai, Artificer, Soulborn, psionics, and the item-crafting system