I love the summonable Blade of Woe in ESO so much, I wanna know exactly how that technique ended up being lost by Oblivion. Maybe the Night Mother decided to withdraw it at some point because the Brotherhood was growing too lax, too complacent, too reliant on special gifts, and lazy children don’t deserve nice things, so it was her way of trying to tell them (without telling them) that they needed to shape up.
But the message didn’t really catch; they don’t know why they can’t wield the Blade anymore, only that they can’t. Some believe that the Night Mother is angry with them while others believe that she’s decided to challenge them by taking away one of their tools. Whatever the reason, they make do with their own weapons and learn not to rely on the handy knife that they never needed to carry but always had access to. But they also start to make their own Blades of Woe and gift them to new recruits with the intention that any murders they’ve already committed have served Sithis indirectly, but upon using their Blade of Woe on their first contracted victim, it is the first blood they have drawn for Sithis. The Night Mother sighs but says nothing. She appreciates the sentiment, but she wasn’t trying to tell them that they need to show Sithis more appreciation, damnit.
After the Purification of the Black Hand, she continues to withhold the ability to call on the true Blade of Woe because while Aerrun has proven herself willing to commit to those hard choices and she and Lucien are both devoted children to her and Sithis, she doesn’t want to go piling rewards on them before they’ve been earned. She blesses the Blade of Woe that Aerrun was gifted by Lucien as a reward to her, but she grants nothing to the Brotherhood as a whole besides a new Listener. Until the Brotherhood has truly earned her grace, they will have to prove themselves.
Then along comes the events of the Great War and oops now the Brotherhood is really fucked. They’re down to a single sanctuary and they’ve abandoned the Old Ways. The Night Mother is by no means impressed, so ofc she’s still not giving them the special knife back.
Only after the Emperor is dead and the Dawnstar Sanctuary is firmly established does the Night Mother tell Lazahk that Daenethys’ ability to call upon the true Blade of Woe has been restored, and that she is to educate the Brotherhood in its use. By surviving what should have been their death throes, completing their contract in spite of the significant challenges, and dedicating themselves to restoring the Brotherhood to its truest self, these assassins have proven themselves worthy of the true Blade of Woe. So long as it does not become a crutch, they have earned the right to wield it once more.