underneath the arches

Arches are an under-used feature in dungeons given their history.  To rectify this shocking state of affairs, here's a table of them since the d12 needs more tables devoted to it's use.

Table 1: A Dozen Arches.

1. Bald arch – Stones show signs of decay.  1 in 6 chance stone falls out for 1d6 damage and 10% chance the arch then collapses, blocking access until the rubble is cleared.
2. Blind arch - Sealed to stop passage between areas or for decoration.
3. Carved arch with dozens of faces. Each face has sunken pits for eyes.  10% chance per dungeon level an obscuring mist reducing visibility to 3' surrounds the arch.
4. Conspiring arch is magically linked to another arch so words spoken at one are heard at the other.
5. Decorated with skulls cemented into the arch.  10% per dungeon level chance d6+4 skulls speak to whoever passes through.
6. Gilded arch with 10% per dungeon level chance of d6x10gp of gold leaf that can be removed (if not it's gold paint or iron pyrite).
7. Memorial arch contains the tomb of a fallen dignitary.  10% chance per dungeon level the tomb still has it's original occupant and grave goods.
8. Natural arch made of a single piece of weathered rock.  10% chance per dungeon level of swirling mists in the arch that act as a crystal ball.
9. Raised portcullis has 1 in 6 chance of falling on unwary.  Winch to raise bars on other side with 50% chance use will draw monstrous attention.
10. Teleportal arch that instantly and safely teleports those passing through  to an identical linked arch elsewhere in the dungeon.
11. Triumphal arch with carvings and commemorative inscription to mark historic event (GM's choice). 
12. Vault – An arched ceiling runs the length of the room.  Drow optional.