First of all, a general advice: stop making new champs lvl 40 and/or lvl 50. Instead, concentrate on some key champs and make them lvl 60, this will be much better for your account progression.

The best strategy for Fireknight is, to bring his shield down with multi hits, and, when this is done, keep it down with turnmeter reduction. Let him get as few turns as possible, best don't let him get a turn at all. Rhazin has a 100% turnmeter reduction on his A3, but unbooked on a very long cooldown, and for stage 14, Rhazin has weak affinity. The key champ is probably the uncommen champ Armiger. Open some green shards or wait until he is aviable at the market and make this champ your next lvl 60. He has legendary quality at Fire Knight and Spider.

A team could look like High Khatun (team leader for her speed aura), Ronda, Rhazin, Vogoth, Armiger. Ronda, Rhazin and Vogoth have triple hits on their A1 and can bring down the shield quick, Rhazin and Armiger have to keep it down as long as possible. High Khatun helps with her speed and turnmeter buff. If you use her in PvE, you should build High Khatun with some accuracy (as a rule of thumb, champs need dungeon level x 10 as accuracy to land their debuffs), so she can place the speed debuff from her A1.

Vogoth, Rhazin and Armiger has to be leve 60 right

i

i

i

How to beat Dark Fae doom tower level 80 with these champions

for dark fae the aim is take more of a nuke team, maybe ur arena team, do NOT put champions like deathknight etc who are going to be hard for u to kill, u want a speed lead, a tm boost and just nuke out ur clones before they can even take a turn, when u reach stage 2 dont cast any spells, save all ur nuke outs so you can land them on boss stage straight away, also if ur really struggling you can appply a shield set to one of ur champions, ur team benefits from the shield, the clones do not.