An Altar in Quake is a wall that must be shot repeatedly to be allowed to continue. This is relatively similar in design to the Unholy Altar, though it has more health and uses a different texture. The Altar is also able to lower itself, much like an Elevator, allowing access to whatever was on top of it.

This barrier does not exist in the Deathmatch version of Prepare for HELL. It can only be found near the final room of said map, behind the Silver Door.