The new mech teased in the re-balance wave 5 announcement had its ability revealed. This ability counters both Deathwalker and Citadel. It's like a little bit of EMP in that it can disable your opponents weapons and ability for a given period, and a little bit of hunter's in that it makes targets take increased damage with some damage bypassing shields. It can't lock your opponents in place nor can it travel between targets or slow them down. But it can make Citadel vulnerable forcing it to retreat. And it's not a movement based ability meaning you can activate it while in Citadel's seismic field. And similarly it can prevent deathwalker that's in its ability from pressuring your team to choose between killing it and not killing it. They can just not kill it because it won't be doing anything to them. You can also combine it with a teammate using Blizzfrost to together turn mechs into sitting ducks while they also take extra damage.

A few notes:

It hasn't been said how much the damage bonus will be. If it will be similar to mark or if it'll be less. Same with shield piercing.

It also hasn't been said how much the energy capacity will be. Though considering it has a damage boosting ability, it very likely will be 24 energy. Though similarly to Blockhorn it's not boosting its own damage directly. So it could possibly be 32 energy.

Now having a legendary mech with an ability that increases the damage a target takes I think that could make running Eclipse more important. It does need an ability duration implant when you run it thanks to double NERF when nobody asked for it to be NERFed in the first place (thanks plarium).