The decayed altar is a regular altar found in level 33 Wilderness during the Summer's End quest. It is located inside a huge cave, and players must crawl through small openings to get to the actual altar.
The altar was added along with the release on the Spirit of Summer quest on 29 July 2008. The Cave plays a pivotal role in the Summer's End quest, released on 15 September 2008. After the quest, the altar can no longer be found and ruins can be found where it was.
- In the altar's room, there are several gravestones. Examining them gives the names of the NPCs (minus the Spirit Beast's name) in the Spirit of Summer quest, including a grave for Summer herself. This cave is actually their burial grounds.
- There are patches of soft soil in the cave, but digging near them with a spade seems to have no effect (players cannot walk on top of them).
- Despite the fact that the altar is decayed, it can still be prayed at.
- There are also remains of fires in the cave, indicating that the caves were used at some time in the past.
- All the graves are made of wood planks, very much like a player's default grave, except for Jennica Bonde's grave. Hers is made of stone, and the only one that a player is able to read fully.
- If you look east of the eastern walls, the Tower of Life basement comes into view, and if you look west of the western walls, you can see a tower of some sort surrounded by a swampy area.