Hellp @Nelloup, welcome to the forums and thank you for reaching out!
Our developers are aware of the disappearing altar issue and it’s being looked into.
Did it occur while upgrading it? Are there any relevant messages in the Event Log?
If so, and as a temporary workaround, some players have reported that staying besides the upgrading temple seems to prevent the issue from happening.
Yes it was during upgrade to level 3 when i loged in in the morning nothing in the log it says altar losing stability but the foundation was 100 percent solid so i see no reason why this occure as it was built properly as you can check my log .And thank you to reply its very apreciated.