Let's talk about Celestials! According to Scathe's tweet [https://twitter.com/lauriegoulding/status/1172912381875249152?s=21], Runeterra doesn't have space like we do in real life. Everything beyond is part of the Celestial Realm. That opens the question on what celestial bodies [Sun, Moon, Stars] even are. I think they are just accumulation of raw unaltered magic that radiate onto Runeterra's sky. It would imply Celestial Magic would be the raw magic, which would fit with the idea of Celestial Magic being the magic of creation like Stem Cells differentiating into different specialized cells, Celestial Magic would differentiate into either Elemental or Spiritual depending on the needed type.
Now to the main part: The Sun and The Moon.
The Sun is the brightest celestial body giving life spending warmth to Runeterra and with equal standing The Moon fulfills its role of purifying the light during the night [Silver Moon -> Silver = Symbol of Purity/Purification]. The Moon is also seen as a symbol of deception and illusion, because you can't trust your eyes under the dim moonlight. [Aribailo made a thread about the Concept behind Sun and Moon which is interesting: https://boards.na.leagueoflegends.com/en/c/story-art/0mEEzrlE-targonian-aspects-of-the-sun-and-moon]
in the aforementioned thread he theorized the Moon stands for Truth, which would contradict my idea of the Moon being a Symbol of Deception and Illusion, but Truth and Lies are like two sides of the same coin:
**"What is Truth?
Is it the truth because you believe in it or is it the truth because someone told you and it fits with your view?
Can you trust your truths?
Are you sure they aren't lies in disguises?"
Something happened between the Sun and the Moon, but what?"**
Here comes my ideas:
**The Moon is a Symbol of Lies, Illusion and Deception. What if the actions of the Moon on Runeterra were just lies to further its own goal and thus angered the Sun?** In Diana's colour story it is confirmed that the Moon can take over its host and override their consciousness, which makes them very prone to be manipulated by the Moon and the Moon not telling Diana the entire story and leaving out parts. I wouldn't question if the Moon was the reason for Diana to travel to Ionia far away from Targon and the newly appointed Aspect of the Sun to make sure she isn't getting the full picture. That would open another question: **What would the Moon be doing behind the Sun's and possibly other Aspect's back?**
Another symbolic power of the Moon is the idea of Purification. **The Silver Moon purifies all, so what if the Moon wants to purify Runterra from the influences of Celestials and the Void alike? An Omnicidal Moon.** But you would then ask why would it do that?
You know the word for madness that is connected to the Moon: _**Lunacy/Lunatic**_. The Moon became mad.
Those ideas would explain why the Solari eradicated the Lunari order. Once the Moon became mad, the Sun ordered the Solari to strike down all Lunari members to protect the world from its madness. If the knowledge of the Moon became lost then no one would climb the Mt. Targon to become the next Aspect of the Moon. The Moon is also a threat to Faith [Sun's concept according to the linked thread above] as the Moon could reveal the Truths of the Celestials and destroy the people's faith. Every time the Moon walks, the Sun follows to slay them to prevent any further damage to the delicate balance of the world.
Now to the Twilight I mentioned in my title.
Twilight symbolizes great change and acts as the Messenger between Celestials. The last time Twilight walked on Runeterra was during the Darkin era. Myisha, the host of Twilight, gave humans the tools to defeat the Darkins and caused the death of some Concepts. Currently Zoe acts as its host to herald the incoming great change. I am suggesting one thing: **Zoe heralds the end of the Moon. The death of Lies and Truths.** The Sun will forever kill the Moon's light to stop its Lunacy.
Fun extra: The Solar Eclipse can symbolize the dimming of spiritual light and the oncoming age of Uncertainty. Without Truth and Lies the world is plunged into an age of Uncertainty!