Easiest is just to run a CC as your fastest. Kymar should work. Sleep them all, then kill them before they can act. 

Just make sure to avoid bringing your tankiest champions in there. You will have trouble killing their mirror images. Go squishy with high damage, to take out the mirrors in one shot. Speed boost, Dec def, nuke. Thats the idea. A coldheart or armiger to reduce turn meter afterwards on Fae is a good idea also

Quite a few ways to go about it with what you have available. Something like Arbiter into Deacon, then CC/nukes to take out the copies, that should do the trick. Ideally you'd want some turn meter reduction too (on top of Deacon), Alure being the best possible option. 

So everyone here has a different method.  I run a TM/CC team with High ACC and Low RES.  Rhazin/Kymar/Ninja with Vogoth/Visix for provoke.

Lots of strats, but basically think about this like an arena matchup. Go first, TM boost, CC the enemy team and kill them while they are sleeping/stunned/TM decreased/etc...

I beated mine with Kymar, scyl and visix.

I tried the stun with Kymar, got the fastest slowed a bit with visix before lose turn and ended up with a nuke. After used scyl to bring Kymar back to life. 

How much speed will I need to ensure I  am first?  TM or CC first?

You will ALWAYS go first, as long as your Turn Meter booster is faster than Dark Fae. When speeds are exactly tied, the tiebreaker is that the Attacker goes first.

So you can have an Arbiter in there boosting into a CC champ with no issues. Or a Lyssandra. Or High Khatun. :)

Here's an example for you of a very F2P team I built way back for the first Dark Fae rotation @ClosedPoly. I also wrote down their speeds then, fortunately. :)

i

I didn't want to go with crazy gear nor crazy speeds, so here's what speeds I ran at:

High Khatun 211

Dark Elhain 182

Kael 167

Ninja 161

Armiger 125  

As you can see CP, I ran with downright slow speeds just for the example. :)

Who could I sub for  Ninja?

Thylessia is perfect, get her to go 2nd to put defense down. She hits hard, and dies fast LOL. Perfect! Good news is, yours won't die, only the copy will

Just to add one more factor into this - not only are you the same speed as your copies, but, (and I could be wrong on this), I'm fairly sure that Whirlwind of Death doesn't "transfer" to your copy. EG if you get kills during the waves, you'll be even faster than your copy will be.

One other caveat to add is - don't forget about other effects. So, yeah, you boost first, but if you're running Maulie to provoke, and you're running Arbiter into Lydia, your Lydia is going to trigger their Maulie's passive, and you'll get cut in. Because that never happened to me.

This boss is such a nightmare. You are all making it sound like it is all over when you kill your original team... its NOT. She always gets a turn. She gets the true fears in. She steals the big damage dealer (= you need to bring two) 

I tried 10 teams or so again like last rotation and finally got this thing down with

Nekmo Taar - Visix - Ragash - Alure - Coldheart.

She never got a turn again after i killed my original team and my Ragash. Since this team is rather low on damage it took ages to kill (15min on DT hard 40 manual)

I turned on auto for a bit but the stupid AI immediately started using stupid skills with Alure and Visix rather than their A1 OBVIOUSLY! Sadly since you got the original fight you cant just program those champs not to use their other skills after the first turn I THINK.

Apparently what works best is using like a Hurndig to slam all of your team one at a time and then do the turnmeter magic with double Alure (i do have a 2nd one at lvl 40 she is in my scarab king farm team right now) 

Personally this is really the boss i want to farm but i just cant do it LOL. I tried last rotation too but never got a team running...

Like i said... if she gets more turns you are basically screwed imho. You need to bring heal reduction for green champs... you need to bring someone like doompriest for void champions i mean i only got 5 slots to bring! ;)