The new ommoran phase is as follow:
The stone will target a random dwarf and encase them in a prison if they’re standing still, reducing the team’s dps for a bit. It also does heavy damage to the drilldozer if the dwarf is standing on it when it happens. This is to discourage camping on the drilldozer.
That’s all there is to it.
I think it’s just some lucky rolls. Personally I only got 1 this season so far.
I did get 2 dreadnought back to back though, so I know how you feel.