The Dramix Altar spawns in groups of 4 in the center of large rooms, 4 times as large as a normal room. It is the second step to getting Dungeon Keys. Simply right click on the top of the altar with a Charged Collector (Obtained from Lord Vatticus for 16 Collector Fragments) and a Dungeon Constructor will spawn. The Charged Collector isn't consumed, so you can spawn as many as you like. Kill one or more of these Contructors to get a key. There is a possibility you can spawn in the dungeon, in a group of rooms that are inaccessible to any altars. In this case the only way to get to an altar room is to enter creative mode, and break walls/doors that are blocking the path.
A Dramix altar