evilruin.wad is a tiny 7-level (each level tiny) megawad for Heretic.  
The maps can be played as single player, deathmatch, and even (but less 
ideally) as coop maps.

Most of the levels were orignally created by Oblige (OK, my own fork of 
Oblige, ObHack); I then expensively edited them to make them better for 
deathmatch play (less camping spots, more connectivity) and single 
player play (easier easier; harder hard).  I have also improved the look 
of the maps (aligning textures; creating new themes; etc.) and have 
added a boss arena to E1M8.

E1M3 is a deathmatch level which I quickly put together from another 
Oblige level (E2M6 from the same megawad as the other levels). I had a 
Heretic conversion of a Doom2 DM level ready, which sadly I can not 
include until I get clearance from the person who made the original 
level (for various reasons, I thought I had clearance, but a more 
through investigation revealed I didn't).  It looks to be a fun little
deathmatch level--I'm improved connectivity compared to the original
Oblige level--but it's quite ugly, with misaligned textures and what
not.  It's a placeholder pending clearance for the Doom2 level (and 
will be cleaned up if I can't get clearance).

It also has monsters, but I'm not sure it can be completed as a 
single-player level.

E1M4 is a Heretic adapataion of a Doom deathmatch level, map06 from 
freedm.wad, by Andy McKie a.k.a. "Mystic", and is part of the FreeDoom 
project.  This map is a tiny 1-on-1 deathmatch level.  There is no exit; 
just warp to another level when done.

The maps have little or no health when difficulty is set to "hard"; use 
"hard" or "nightmare" difficulty if you want a level (almost) without 
health when playing deathmatch.  The easier difficulty levels give you 
progressively more health.  E1M4 doesn't give you health at "medium" 
difficulty, but doesn't have powerful weapons the way "easy" and "hard" 
do for this level.

The maps have not been tested in deathmatch.  However, single player 
play has been extensively tested; all SP maps have skill levels, are easy 
at "easy", somewhat challenging at "medium", and very challenging (but 
possible) at "hard".  All levels can be completed starting with just the 
wand at Smite-Master difficulty; in addition, all five SP maps can be 
finished with 100% kills starting from the beginning of the game at 
Smite-Master difficulty.  Whether is is possible to finish E1M2, E1M9, 
E1M7, and E1M8 at Smite-Master with 100% kills starting with just the 
wand is an open question.

The maps are optimized for Doomsday 1.8.6; they are also compatible with 
and have been tested in the original DOS Heretic.  Note that the current 
(at the time of this writing) 1.9 beta of Doomsday does not work with 
these maps; this is a Doomsday bug and not a bug with the maps.  The 
maps have also been tested and work in GZoom.

The maps are designed to *not* use any non-DOS-Heretic features, such as 
jumping.  It is possible to finish all of the levels without a mouse, 
even at Smite-Master difficulty.

The maps replaced are E1M1, E1M2, E1M3, E1M4, E1M7, E1M8, and E1M9.  
E1M2 has only a secret exit; this allows the maps to be played in order 
and see only the five maps suitable for single-player play.

In more detail:

* Reasonable difficulty levels.  Easy is easier, hard is harder.

* Better starts; make sure we're not facing the wall or anything.

* Boss arena in E1M8.

* Better stair textures; ObHack does a bad job with these.

* Non-right angle lines, to make the map look more natural.

* The outdoor water areas look really bad in ObHack; waterfalls added.

* Wider staircases and less things that block your running around.

* Less hidey holes; let's discourage deathmatch camping.

* Better secret entrances; now you have to actually pay attention to
  find the secrets.

* No super-tall lifts 

* Extensive retexturing; the textures are actually aligned and I've 
  added a couple of nice-looking new themes.

Here is a description of the megawad:

* Game: Heretic (hopefully is compatible even with DOS version)

* Episodes replaced: E1M1; E1M2; E1M3; E1M4; E1M7; E1M8; and E1M9 (E1M2 
  has only secret exit, since E1M3 is deathmatch-only)

* Single player: Yes

* Co-op: Somewhat.  The maps are optimized for SP and DM; but each map 
  also has four coop starts.

* Deathmatch: Yes, oh yes (I think.  Not tested, but I've gone to a 
  lot of effort to minimize camping spots, improving connectivity, and
  balancing deathmatch play.)

* Editors used: Oblige/ObHack made the basic layout; extensively edited by
  hand in Doom Builder.

* Map size: Small (Small enough for 1-on-1 deathmatch but can probably be
  played with up to 4 players)

* Story: Plague and misfortune have come upon the land.  It started when
  magicans in Tixacan performed forbidden dark magics, opening a portal
  unleashing forces of darkness in to this world.  Tixacan is now in ruins,
  all of its people dead, overrun with unspeakable evil monsters.  The 
  monsters are bringing pestilance and suffering in to this world that is
  spreading.

  There is a magic around the cursed area that makes it impossible to 
  bring in anyone to destroy the evil there.  Our greates magicians have
  studied the magic, and they can open up a hole that only a single person
  can enter.  You are that person.  The hole is small; you can not carry 
  great weapons through it; you can only bring but a single wand. 

  You must enter the ruins of Tixacan and find the gateway opening this 
  world up to the unspeakable forces of evil.  That gateway must be closed.
  You are our only chance; if you do not succeed, the world will be overrun
  by unspeakable evil and all hope will be lost.

  (Co op story: We can only let two or three people in through the magic
  hole in to Tixacan).

* Deathmatch story: Same as above, but they were able to let two or three
  people in the city.  When you entered the city, instead of finding it
  overrun by monsters, you instead find it deserted.  But now you are losing
  your senses.  Anger and hatred consume your soul, and you are unable to
  resist it.  You want to do nothing more than kill your closest friends who
  came in with you to fight the evil here.

  There is a force here that lives on human emotion: Anger, resentment,
  enmity, hatred.  It has consumed you; it feeds off of your anger and
  violence as you kill your friends.  When they kill you, instead of
  dying, you come back to life; the evil force that feeds off of your 
  hatred keeps you alive to give it more life force.

  You are now trapped in an endless cycle.  However, even though you can
  not stop the anger consuming you, you can go deeper and deeper in to
  the ruins of Tixacan until you find the gate that links this world to 
  the world the force of evil resides in.  But this force will only let you
  in if you let it feed on your anger; so you give in and kill the people
  you came here with as they kill you, only to be brought back to life
  to continue the cycle.
  
