How far back acloudyskye's world goes
Genius shows acloudyskye's first song to be Runaway, dating back to October 14, 2017.
The first time Enth shows up is in Spaces, from December 31, 2017. Enth doesn't show up again until Parting Gift (April 15, 2018), then starts consistently appearing in When There Were Others (August 4, 2018) and onwards.
As for videos, the first one is At Rest (February 15, 2021), part of Blood Rushing Like Current Through a Powerline.
Ila's arrival seems to be hinted at in Somewhere Out There, also part of BRLCTAP. Ila arrives in FIRST ENCOUNTERS (March 5, 2022), although is pictured earlier in Daze (November 18, 2021), and is only let in by Enth by the end of What Do You Want! (September 2, 2022).