I’m posting this here since I’m on the test patch and I’m not sure when this change occured.
In earlier versions of the game, Grava’Thul could not spawn until you killed Ekket’Zul in the Void’s Edge. Iirc the reason for that was the first Rylok boss you’d encounter shouldn’t be a Nemesis but a regular story boss (in this case the final boss of Act 5).
However, as I was just progressing the main quest through Act 4 on Ultimate, I encountered both Benn (as expected) and Grava in the Seal of Loghorrean. As mentioned before, Grava should not appear until you beat Act 5.
btw on this character I skipped Normal, started on Elite but did not kill Ekket’Zul there either, so in theory I should never have triggered the condition that allows Grava to spawn.
Is it a bug, an oversight or actually intended?
Also yes, I’m aware of the new Nemesis spawn system that got rid of fixed spawn points. Doesn’t explain why Grava can spawn before killing Ekket.