This is my full walkthrough of the end game (Ancient Ruins/Glass Desert). Along the way you will pick up the five achievements listed below. For this achievement you will have to go through the Ancient Ruins and to the end of the Glass Desert to get it, so you may need to watch the whole video, but here is where the achievement pops:
17:30 Achievement: Doors Like These (read final note)
Right after this you should have all the letters and can get:
17:43 Achievement: The Adventure Continues (read final letter at Ranch)
The Renewal achievement in Slime Rancher worth 43 pointsStart bringing life back to the Glass Desert