The Altar of Elements is a Big Decor introduced in the 12.0.0 update.
It appears to be a stone stand with 4 blocks: one is for winter, one is for spring, one is for summer and one is for wall. The block in the middle has all of that.
It is used to tremendously increase the efficiency of Gadgets.
- This can be found in Four Seasons, which is currently a removed map.