I feel like this post is missing the "What are eternals" paragraph. There's a lot of why how and when but no what.
Lots of good info about "what it is" over here https://twitter.com/KenAdamsNSA
This thread was added on August 13, 2019, with posts from MoreChrono.
Original Post
https://nexus.leagueoflegends.com/en-gb/2019/08/dev-exploring-eternals?t=1565715280948