If your current champs aren't even getting a chance to fight, it's likely that fixing that will be an easier route to winning than bringing in new rares who aren't even leveled and built yet. 

Your Frozen Banshee, if built for clan boss which I assume is the case, should be fast enough to at least get one hit in before the boss, putting poison sensitivity. If your Maus Mage is also fast enough to get a turn before the boss, he could put block debuffs and increase def on the team, which should ensure that nobody gets a fear debuff and you take less damage from the boss' AOE, then on the next turn FB can put two poisons on the boss and you will already be a good part of the way there. Corpse Collector could add extra poison or try to put a Leech, which will help keep your team alive. 

As for UH rares that could help: Seducer, for decrease attack (though sadly only the weak version) and some team buffs. Gravechill Killer for decrease defense and more poison. Doomscreech for speeding up the team while increasing defense, as well as a decrease accuracy. Grinner for his aura and a revive. There may be others. 

Oh, and also, do this on manual and make sure your champions don't use their important skills on the first two waves, or use them early enough that they're off cooldown again when you get to the boss. Then once you manage to kill the boss once, move on to the stages after that which will be easier again. You can come back for the 3 stars later in the game, like when you have a bunch of 6* UH champions. 

Thanks for the tips,

right, part of the problem is that my team show up after the waves have already tuckered them out, and they get put to sleep.  I am not savvy enough to manage complicated action manually.  My Maus Mage has 35k power but he just melts away in seconds.

as far as meeting the Boss, I cannot get past the two sidekicks or even hit them in any meaningful way...

I used to have Seducer, gave him up.

first six levels go by real easy, must be the Boss is a whole nother animal.

I notice in other factions that L8, 9, 10 are much easier than L7.

Yeah, those boss levels are always harder than the rest, for sure. But the first two waves before the boss should be doable enough, so you can keep your important skills ready? And speed will make a big difference here - if you can debuff the boss, or buff your team, before the boss even takes a turn, it can increase your survivability drastically. 

I'd ignore the sidekicks honestly - they don't do that much and if they die, the boss will get them back up anyway. Focus on the boss - once the boss is down, you'll get the win, whether the sidekicks are alive or not. Same as in Ice Golem. 

Seducer is a very good Champion.

I use Seducer in my Auto Farm Stage 20 Team.

I use Seducer in Stage 21 Team.

My Stage 20 Team is the following:

Leader: Seducer

- Gorgorab

- M. Mage

- Harvest Jack

- Rotos

I can beat Stage 21, but I haven't been able to 3 star it.

I keep getting bad RNG.

My Stage 21 Team is the following:

Leader: Seducer

- Gorgorab

- Elegaius

- Zelotah

- Rotos

Stage 21 Boss - Ignores Defense.

Stage 21 Boss - Does annoying Debuffs

Seducer has a Health Aura which is great to keep your team alive.

Most times you want to use Defense Aura, but the Boss Ignore Defense so the Health Aura rocks.

Seducer has Block Debuff Buffs which last 2 turns.

M.Mage can do Block Debuff Buff, but his only last 1 turn.

I tried using M.Mage for Stage 21, but his Block Buff can't expiring to fast on my champions.

They ended up getting feared + stunned.

It was super annoying.

FYI- my 3 champs have a total power of 66k.  Mage is fully booked, speed 175.  Frozen is barely booked, speed 135 but I can get it up to 150.  Cor[se is barel;y booked, speed 154 but I can get to about 170...which one should go first, second , third?  That is something I can understand and deal with.

I wish I was savvy enough to follow those tips.  Which are my "important" skills?  Ignore the sidekicks---How?  They are just banging away at me without me doing anything.  Don't you have to defeat the sidekicks before your attacks get to the boss?  You must live in a world where all your speeds are 250 or 300.  I have a hard time getting to 150.

You said before that my frozen banshee should be geared for clan boss, it possibly is by coincidence but it is nothing I tried for or even knew how.  But she gets wiped out easy.  I am using offense, crit rate, and perception artifacts.

In a faction fight you are limited with who you can use.  Other than M Mage I do not have any of those other big names in show business.  No gorgorab, zelotah, rotos, harvest jack, m monster, any of those.  I guess when you are FTP they put a censor filter on you so you do not get anything good.

L7 is my L20 right now lol.  With all my shortfalls I do not know where to begin.

I am f2p , dont get no real good pulls but i stil got togather pretty decant team and i "stuck" on lvl 19 cuz my dark athel is only 50 with a "poor" gear and few books. But anyway, this team drive me from 1 till 19 without any problems. 

Gorgorab. Zelotah, Mausoleum mage, Frozen banshe and Dark Athel

Need to work on my Dark Athel, but there is hardly any "time" for her 😹

Try to put at least something "similar" togather so you have in your team a little bit of everything 👍

I wouldn't recommend at this stage of the game that you start building champions specifically for faction wars, that wouldn't make sense. But I would definitely recommend you to improve your Frozen Banshee build for CB, meaning getting her books to max her skills, masteries (warmaster and master hexer are the key ones) and enough speed, which will also help you then in FW. My FB has 177 speed, much faster than the stage 7 FW boss, which makes that fight a lot easier. In terms of her other stats/gear, you may want to get her lifesteal gear (only after she gets warmaster, it won't help much before that), other gear more aimed at defense/HP. FB is a pure poison champion, the only thing that matters is that she puts her poisons (so high accuracy and sufficient speed) and survives to put more poisons (so hp/def). 

Your important skills in this case are mainly FB's poison sensitivity, Mage's block debuffs and heal. Those should be off cooldown when you get to the boss, so FB can immediately start to put poisons and Mage can buy the team some time by blocking the initial fear debuffs. As for ignoring the sidekicks - just don't attack them. Click the boss for any offensive skill you use. To be clear, that approach definitely doesn't always work - some other Faction War bosses or dungeon bosses get a ton of buffs from their minions and are basically unkillable until those minions are down. But it works well here. 

I would love to have a gorgo, know where I can get one?  The game won't give it to me.

Just an update to my original post, and to declare Success on beating that pesky Boss on Stage 7. I got some good advice from here and wish to extend credit to whomever it is due.

In addition to my first 3 champs of M Mage, Corpse Collector, and Frozen Banshee, I acquired some others in UH: Hollow, Defiled Sinner, Skullsquire, and Rotting Mage. My teams are always evolving, I am trying to make 13 faction teams of 5 champs each, so as better ones come along I use those.  After some testing, I found that Defiled Sinner and Rotting Mage held the most promise.  I was able to start knocking the Boss back bit by bit, and kept upgrading their levels and artifacts as it looked beneficial. But I also had to alter my strategy, in order to save my better skills for the Boss stage I had to take the battle off Auto, and use only A1 skills  manually.  I also focussed only on the Boss and ignored the 2 sidekicks.  I finally put enough together to beat the Boss, and win the Rare book, which I gave to Rotting Mage.

The following Stage 8 I was able to win easily with 3 stars on Auto...go figure.

So thanks for the good help I received.

Hi, here is a very good break down on Faction Wars team composition and generally one of the best Youtube channels on Raid by HellHades:

https://www.youtube.com/watch?v=HTgyFxa8nSY&ab_channel=HellHades

Hope it will help you progress with your Faction Wars. Was able to beat this pesky boss today as well

Undead team power 227k...main team power rolling in the 320s  brutal dk 13mil....able to help on hyrdra....undead faction 7? constantly one shotted....a goal I gave up on

my 5 cents to the thread - 1st boss is annoyance because easely kills anyone I can send. what helps me:

come to boss with all skills ready - currently can just A1 stage 1 and 2 and get no damage to my team;

UDK lvl6 higher speed than boss to start battle with shield all

other 4 chars are 4-star and do what they can - concentrate hard-hitters on boss because he has relatively low HP, does not heal but it resurects minions if they killed, so freeze and stun minions (they hit hard), killing one of the minions (using mass-nuke and then someone just finishing them) would help to distruct boss from attack to resurect minions...

Finally beat Undead FW stage 7 myself.  Had never tried it on manual because there's always so much to do that I didn't spend the time to try and figure it out, but got the "beat a FW boss" advanced quest, so figured this was a good time to try and make it happen.

My team as Gorgorob lvl 40, Dark Elhain lvl 40, Ultimate Deathnknight lvl 60, Gravechill lvl 50 and Frozen Banshee lvl 50.  My speeds weren't so great and the boss got to go first.  Previously, I always had UDK as the team leader and he would be annihilated immediately by the boss.  This time, Gorgorab was the team leader, he too was immediately annihilated by the boss, but that meant that UDK was left alive to throw up his shield.  Once I survived the first round and getting feared, ignoring the sidekicks everyone just focused on the boss and UDK with Warmaster put a big hurting on him. 3 of the team went down, but they put up enough of a fight for UDK to carry the day.  Having higher speeds will definitely make it a much easier ordeal.

I then immediately auto 3-starred levels 8 and 9.  I'll come back to 3-star the boss much later.  Just happy to get to the higher levels to get better glyphs.

I tend to just try and auto everything in the game.  Obviously, in this case, that's not the way to do it.  Thanks for this thread to help me get by this boss.