Here is another installment of exTRAPaganza, our Thursday over-the-top trap series.
A large concrete wall is ahead. Centered in the wall is a single iron door.
The door radiates strong magic.
The wall is cool to the touch as is the door. The wall is the base of a dam. The door is an old service door that was magically sealed after the dam was made. It cannot be opened unless a high-level DC is made with dispel magic. However, once the magic seal is removed, the door flies from the dam as water rushes in, which also causes the dam itself to collapse. This sends billions of gallons of water into the area and above, along with millions of tons of concrete.
I’m sure there is some kind of save… But half of a million points of damage is still a lot.