Seeing Herma-Mora pop up in Tamriel to go all tentacle on Storn got me thinking. Granted, this was probably not Herma-Mora's physical form (like Mehrunes Dagon in Oblivion) and maybe an aspect (like Hircine's in Bloodmoon).
But since there isn't a Septim heir anymore to wear the Amulet of Kings and the Dragonfires are not lit anymore -> why hasn't any Daedric Prince (and in particular, Molag Bal and Mehrunes Dagon) invaded Tamriel anymore ever since Oblivion ended? Is there still anything deterring them?
Or was Herma-Mora merely able to enter Tamriel because this was during a prophesized event likely mentioned in an Elder Scroll? IIRC Hircine was able to physically manifest during Bloodmoon, but chose to fight the Nerevarine as an aspect.