To use the Grand Lift of Dectus in Elden Ring you need two Medallion halves that can be found in Fort Haight and Fort Faroth. You can reach the Altus Plateau easily once you have them, saving you the ordeal of the alternative route that's both hidden and dangerous - finding the two Dectus Medallion locations might take a bit of searching but it's by far the better option earlier in the game. There are reasons to take the alternative route, but it's best saved to later.
So, to help you find the Grand Lift of Dectus Medallions and get the lift working we've got all the info on where to go in Elden Ring, what to look for, and what the stages of getting the lift working involve. We'll also cover that more dangerous route, if you want to risk it and show you how to get to the Altus Plateau without using the Grand Lift of Dectus, just so you can make your own decisions.