Eostrid, but I'm super curious what @ShortOnSkillz thinks. 

put it like this, got Eostrid at 50 ready too 6star tomorrow, owl features is still roosting in my summoning portal

Point Taken. Hard Hydra it is. I do not run a team on Normal either.  As to Eostrid vs. Gwyndolin, I would use both of them:  

Gwyndolin goes in place of Gurptuk and brings significant additional Damage & Leech. 

Eostrid goes in place of Arbiter, and brings s-tier passive healing...unless you still can't stay alive?

I run a Hard Team w/o a Reviver,  so I know this is doable.   

Hmm. That's an interesting option. Arbiter really is mostly dead weight on the team, after all. Okay, time to use some lego books lol.

You totally could try Razelvarg in place of Gywndolin before sinking books into her (althoguh I do think she is worth building).  

Razelvarg brings leech, big damage, offers the 20% speed aura, and you have him 6S awakened.

Unless there is somewhere you specifically want the Phantom Touch, I would switch that to Soul Reap in a heartbet.  He'll be reaping every Hydra Head that Trunda hasn't already killed. 

The big thing that Razel *doesn't* bring is the speed down. And, given I already have the speed up from Lydia, I'd question whether he'd help hugely there. Though the Soul Reap is a fair point.

Crushing Rend if 6star, no?

Razel's running phatom touch mainly for my FK H10 team. 6* gives him two extra hits against the shield, which helps quite a lot to ensure I don't get a loss because of some bad luck rolls.

Id probably try Gwyn first.  Eostrid would burn turns that should be going to Trunda and doesn't bring much additional utility outside the Decrease Speed since you're getting everything else in her kit from someone else. 

If you tried Eostrid & Rabbit, you'd be getting the decrease speed from Eostrid.

The extra stats from the 6S Awakening means that you can get a much tankier build on the Rabbit than you can on the Owl.

I am not sure what @ShortOnSkillz is going for on not trying Eostrid.  If Eostrid is going in place of Arbiter, she brings the Inc Atk that you want to have as well as offering better utility for the entire fight (except no revive).

He may have just answering the Gwyndolin vs. Eostrid question, and if so, I agree with him.

However, I really think you could do this w/o Arbiter and then you want Eostrid and either Gwyndolin or the Rabbit, but I would lean to trying Rabbit just due to the extra stats.       

Yeah, maybe.  I don't have any 6 star Crushing Rend toons, so can't say for sure.  

I may have missed a piece but yeah I was commenting on Gwyn v Eostrid within a team of Trunda / Gurp / Lydia / Arby.

Always.  Though I have seen some people say even at 5* it's okay.  Something to do with exposed necks and respawned heads act as new enemies so CR resets when that happens.  Havent tested personally.

So, I'll be tryin these ideas out eventually, but not until the next fusion, since I don't want to waste valuable champ training points atm. In the interim, I'm going to give Razel a try. Regarding his blessing, I'm not convinced on switching him to Crushing Rend, primarily because he's very much not geared for damage atm (due to his role on my FK H10 team). He's currently at 4.2K ATK, 39% CRATE, and 192% CDMG - and 353 SPD.

Given he's not really built for damage, I'm debating either swapping to Cruelty (to boost Trunda even more) or  Soul Reap (given it scales on enemy HP, and not on his own stats). Thoughts on which would be better? Or to just leave on Phantom Touch. (And yes Wiley, I see you already suggested Soul Reap)

And what kind of sets of gear has each of them, please?

If Rabbit isn't built for Damage, I would concur that Crushing Rend probably isn't the right choice. You may want to just leave him with Phantom Touch, especially if you need the extra hits for FK.

However, maybe a Mod could answer this:  If a different member of the team hits a Hydra head and brings their HP down to19%, and Rabbit hits them, but doesn't kill them, will the Reaper still proc, even if Rabbit didn't actaully bring the HP under 20% himself?  If the answer here, is "yes", then Soul Reap might still be a good option.

Having Cruelty on the team is always good.         

if reap isn't on cooldown and the hp threshold is below where it needs to be to reap proc, it will proc a reap attempt.

That's how I thought it would work.  Thanks.  

I have a similar issue to kram really, but i recently pulled my 3rd trunda.

I have been using a yumeko-trunda-trunda-lydia-arbiter-nekmo team on hard which is decent enough  damage on hard but is nothing like the 2-3 billion damage scores i see online.

I have been toying with either putting nekmo into a cursed set as there is no hex in the team, or maybe looking at a triple trunda team?

things you'll want (bit of a tl;dr because I'm trying not to miss anything): 

at least one cursed set

consistent resets on trundas 

good damage sets on trundas (6 pc merci + zeal with a bloodshield accessory is the current tops, but ignore defense 4 pc sets + zeal with bloodshield is good too)

9 piece protection is good on lydia

high stat Cruelty on one of your AoE champs, preferably A1

Crushing Rend on 6* Trunda, Heavencast otherwise

I wouldn't run a third Trunda, I'd look at bringing in a Lanakis to lower crit rate on the builds, or another reset champ like Kymar/Nia and likely get Nekmo out. He's probably eating too many turns.