The line about 'These violent delights have violent ends' definitely seems to be a trigger phrase to the hosts. And that shines a new light on what Ford says to Lowe after Millay breaks down:
'The problem, Bernard, is that what you and I do, is so complicated. We practice witchcraft. We speak the right words, and we create life itself. Out of chaos.'
This seems to be a clue that Ford himself who installed the trigger phrase, especially because he says it right after Lowe theorizes that the photograph alone shouldn't be enough to cause Abernathy (Delores' father) to glitch. It's important here to keep in mind that it was also Ford who installed the "reveries" that's causing the hosts to "remember" their past as well. It's probably all part of the big "game" he's trying to set up in the desert near the buried church steeple. There seems to quite a lot of history there, since the first time we see Ford at the place he's shuffling his feet through the sand, as if he's trying to find his footing on what has been, figuratively but also literally, buried below.
That's another scene full of important clues btw, as Ford asks the boy if he can't imagine the town with the "white" church at the "nowhere land". The buried church steeple after all, is black(ened), another hint at the past being buried there. And the boy of course, is a host based on Ford as a child, a means perhaps to converse with his past, with the innocence and excitement and wonder he has lost. Which he also hints at with this line:
'Everything in this world is magic. Except to the magician.'
Ford is the magician after all, and I think he's become bored by his own creation. So his end game is to make the hosts' AI advance beyond the sum of their programming. To have them rise above what he made them, so he can be amazed again.
There's also the other side of the coin, the "game" the man in black is playing and the maze that, according to the little girl, isn't "meant" for him. But in the same scene we see the security chief say that the man in black gets whatever he wants, and the man himself explains that he's been in the park for thirty years, ever since he was "born" there, hinting at the man's place and past with the park. But if he is pretty much given free reign, yet the maze isn't meant for him, there are only two options. Either the man is in fact a host after all and the maze is only meant for guests, or the man is a guest but the maze isn't meant for guests. Now since the latter seems most obvious with what we've been given so far, that begs the question, if the maze isn't for the guests, what is it and who is it for? It could be that the maze is in fact the same place as the buried town at the "nowhere land", the hidden, long forgotten past of Westworld that they have built a new world upon, but at this time, that's all a big mystery.
And of course there's good ol' Delores, who we find out here has indeed advanced far beyond the other hosts, and this fact is at least in some ways known by Lowe who secretly converses with her, but even he doesn't realize how far as she is clearly still playing along with the script, to answer the question asked by
@OnFleekTing above. Because we know she understands how the trigger phrases work and what they do, and we know she's already scheming. And as we see with Millay being able to (accidentally) wake herself up from a programmed sleep mode, there are multiple ways to overcome one's programming. The thing is, only Delores is currently aware that she's being programmed, so she's the only one able to take proper advantage of this.
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