Must admit to scratching me head with Lyrazsa’s Lair…
You have a 1 in 3 chance of casting a spell that does damage with 1 troop of the 4 faction troops, Lyrasza.
So, your only method of winning is raising attack on your Dementicore’s and skulling down. You could argue that you have about a 1:100,000,000 chance of winning running anything else, which is generous imo 
If you have no other damage, how do you actually beat infernal armour?
Infernal armour crops up with Bone Naga and Wall of Bones.
Walll of Bones gains 125 armour boosted by undead allies and enemies, so usually gets about 140+armour if it casts. It starts with 900+ health. To hit it with skulls at 250 hoard with 50% bonus, you do 120-128 skull damage give or take medal choices.
So, with infernal amour reflecting 25% of skull damage, with 128 attack, it’s hitting me for 32 a go. As soon as that raises, it’s usually 72 attack stolen - 200 attack and 50 damage a go. It outheals one skull hit each time it casts.
So, it needs to be hit 8 times without it casting at all for enough to = take it to 0 from starting health. In that time, without any other damage, it will hit your troop for at least 240 and probably 320+ damage from your own hits. There is zero chance it won’t cast as it is 10 mana cost, and purple. Lyrasza has a purple and blue storm, so it’s going to fill AI a lot. It also has Grave Seer in the ranks an empowered green to purple converter…It also has Skeleros waiting to double skulls and blow up your team.
So, I can stop Skeleros by using Dementicores on it, with luck 1 in 2 casts will drain or silence it. I can slow down Grave Seer, but it usually self enchants itself (or Wall of Bones if you don’t hit it) and Wraith, I can possibly ignore to some degree. I can’t do anything about Wall of Bones, my only option is hoping Lyrasza will cast her spell 100% of the time and knock off 160 health, but of course Wall of Bones self heals that.
Yesterday I came up against it in the path to the boss. I looked at the first 2 choices, and it seemed the only option from what else was on offer - Golems which always take out the first troop.
Today it was the below
The room was Marilith/Scale Guard/Tai Pan/Bone Naga
It was one of the first rooms, created at the start of delves.
I can’t win this battle without stealing attack. I can’t use any other troop than I have because it is impossible.
Just spent 5 minutes avoiding skull hitting it, each Lyrasza cast was a board shuffle. I had to kill 3 troops to get here and my own skyfall skull killed me… as my 1 in 3 chance of spells with Dementicore raised my attack.
I can’t not raise attack because I can’t kill anything without it… I’'ve shut it down to 31 attack and silenced it, and just died by skyfall skulling it.
The problem is by avoiding 2 more rooms on the run to the boss, your options are limited because out of all of the available rooms, most are also impossible.
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