MAP21: Avenger is the twenty-first map of Community Chest. The level is set inside of a town invaded by demons, who you must kill in vengeance for the town's destruction. It was designed by Sphagne, and was originally released standalone. It is the author's tenth level. It uses the theme song of HereticE1M6: The Cathedral.
In the room east of the starting area, a section of the hole in the southern wall with a candle sitting on it counts as a secret. (sector 35) However, it is impossible to trigger, as it is too small for you to step on.
Enter secret #1, drop down, and quickly run into the compartment to the west before it closes to obtain a box of shells. (sector 435)
In the room east of the starting area, the alcove in the north contains a pair of Cacodemon corpses. To the west of them is a stairway. Enter the hole, go down the stairway, and then hit the switch in the northwest of the next room to find a soul sphere. (sector 65)
In the room west of the starting area, run up to the yellow door, and then enter the northern room. Enter the hole that has opened in the western wall before it closes, and head along the walkway. At the end of the path is a pair of rockets, and a rocket launcher. (sector 332)
At the end of the tunnel south of the library, there is a large gap separating the tunnel and a set of rocky steps. Jump across this gap, and climb up the steps. In the northwest of the next tunnel is an alcove containing two cells and a plasma rifle. (sector 383)
Enter secret #5, and then go back down the steps, and onto the lower floor, to find a teleporter leading to the southeast of the level. (sector 385) This secret, located in the sector before the teleporter, is hard to trigger due to its small size. It is best to enter the sector as slowly as you can.
In the marble room in the northeast, there is a flight of steps leading to a medikit, a box of ammo, and a chaingun. From the apex zenith of the stairway, jump to the platform in the northwest of the room. After this, drop into the hole, and you will obtain a berserk pack. Walk forward to find a teleporter with a box of rockets sitting in it, as well as a switch. (sector 267) Flip the switch to lower a pillar holding combat armor. Enter the teleporter to return to the marble room.
After flipping the switch that lowers the red key, climb onto the railing, and walk along to the eastern pillar, which bears a switch on its eastern side. Flip it, and jump down to the east side of the room. Run into the opening to the north to enter a secret hallway leading to a bulk cell. (sector 134)
In secret #8, a portion of the northern wall has white markings on it. Open it to find a lift. Take the lift up to find a box of rockets and combat armor. (sector 295)
Because you cannot step on secret #1, you can only obtain 88% Secrets on this level.