This is my suggestion on how to make Xathenos viable.
Xathenos is the second hardest troop to craft right after Zul’Goth and yet he is the least utilized mythic in the game and practically useless. The main problem is his 1-3 random undead summon. There are not a lot of good undead troops available yet and most will mana block him since he is best placed near the bottom. No one wants to put together a team that is unpredictable with troops that have no synergy. At low level play this might be okay, but no low level player can afford to craft him anyways (I’m lvl 1,192 and only just got enough resources to craft him).
So, my suggestion is to give him a single undead summon of a higher rarity troop and a better buff than say immunity to devour.
For example, Skadi summons Mab, Weaver summons Webspinner, Abynissia has an Infernal Knight. Each of these mythics has a guaranteed legendary summon that has some synergy and is more powerful than almost anything you are likely to get from Xathenos who summons only when enemy dies. Granted, he has a powerful attack that gets stronger each time, but he is supposed to be more bad ass than normal mythics, that’s why he is so hard to craft. So give him some decent summon that won’t mana block him (i know that’s a tough one) like Crimson Bat, but hell even the Wight would be better than random, true damage, no mana overlap, generates purple, perfect for setting up another attack. Obviously less powerful so balancing would decide which.
And in exchange for the summon reduction, make him more useful by adding something lore friendly like…
death marks! I would do a trait like death mark all enemy troops at start of battle; or a random enemy on 4 & 5 matches or when matching purple. If that’s too much, than add to his attack death mark the enemies on either side of his target, but also add to his cast something like a 50% chance to kill a single death marked enemy troop. It’s still a lottery like summoning random units and shouldn’t be op since death marks have a small chance to kill and you recover from them easily.
Maybe do the death marks if summon is wight but not with crimson bat or play with the chance to kill death marked percentage for balancing.
So this is my idea, let me know what you guys think, I would love to use this troop but right now it’s just not worth the amount of resources that he costs and no one crafts him or uses him even if they did. A missed opportunity for an awesome troop.
EDIT: I had another brainstorm to put forward. If you guys don’t want to get rid of the 1-3 random summon for lore friendly reasons, after all he is the lord of the undead, makes sense he would summon a lot of undead. So how about keep it but add a trait that allows all undead allies (including the ones he summons but maybe not himself) to either start at 50% mana or even cooler, start with enchanted status. That would be unique as no other troop has that ability and it would mitigate some of the mana blocks, since most undead use brown or purple.