Ok, I'd like to rescind my previous cynicism and propose an actual hypothesis for the existence of the kill phrase.
I don't buy that Lenore is suicidal, because people with suicidal ideations don't make long term plans or set long term goals. She might have felt lonely and depressed but she still kept on going with her research. She even planned a trip to Baldur's Gate and likely went through with it.
My hypothesis is based on two facts. 1) Lenore built a way for her automaton to kill her. 2) She had the exact ingredients in her lab to brew Omeluum's potion.
Hence my guess: Lenore was infected by a tadpole, but found a way to keep it in stasis, effectively stopping the ceremorphosis. However, she knew things could go wrong and decided to install a failsafe into Bernard. Should she start feeling the symptoms, she would say the phrase and have the automaton stop her heart with a single, painless blast of electricity.
After all, that's the exact strategy Nettie suggests with the Wyvern potion.
Bravo! I also do like this theory. I will say that sometimes it amazes me how much detail they put into this game in certain aspects. It is clear that Lenore never intended on leaving permanently. She was just planning on going on a long trip that would be several months in the making. She said she planned to be back by the end of the year. Her research was extremely important to her. It was the most important thing to her. She was willing to sacrifice just about everything to see it through. So I really don't think she would have committed suicide at least until her research was done.
So it is likely that Lenore died in Baldur's Gate and that's why she never returned. Whatever she had completed as far as her research was most likely stolen, meaning her ring that she mentions. So if she was the first with a tadpole in her head, that would make a lot of sense and tie it all together.
One thing that still puzzles me is the damage done to her Tower. The top two floors are extensively damaged as if something massive tried to break into the tower. At first I thought that maybe her Tower was just not completed, but then I noticed during my last playthrough that that was not the case. It was almost as if a giant airship crashed into the top of it, damaging the top two floors. If someone or something try to invade her Tower from the top down that would explain why the towers only guardians were on the top level. They were up there to repel Invaders. But if this is the case, where are all the bodies of those that might have invaded? Did Bernard and the animated armors dump the bodies off the top into the lake?
Either way, I really like your theory. That really makes sense as to why she would create a kill switch phrase. Being so intelligent, if something went wrong she would want her guardians to kill her. She seemed like that type of person.
