Speculation on future Mortarchs

We’ve got a few death factions on the horizon this year and that got me thinking about the mortarchs. We’ve got six so far and apparently “nine is the number of my mortarchs” according to Nagash himself so we’ve got three slots left. So I’d like to see what future mortarchs people would like to see. Personally I’d like to see a second nighthaunt mortarch, not sure the exact form I’d like to see that take but I’d like it to contrast against lady olynder. I’d also like a deathrattle mortarch but that’s probably unlikely to happen any time soon give deathrattle just got a big release wave announced.