But how could he do it, either way? Sotha Sil's contract with the Daedra was sealed at the end of the First Era, wasn't it?
...And aren't the eight towers that are (supposedly) preventing Nirn from collapsing into Oblivion all doing just fine during the Second Era as well? I mean, considering it's established canon that most of them are still around until the Morrowind/Oblivion years, when they all started dropping like dominoes...
Unless there's some hidden piece of lore I'm missing. Or, you know, somebody accidentally bumped the off switch on them at some point during the Second Era.