Scourge of Amragon

The Scourge of Amragon was the first expansion pack to Quake; one of two official mission packs, it was created by Hypnotic that would later reform into Ritual Entertainment and then died a slow death from there.

The pack starts you out in a human base and the level progression has you fighting your way into Aramagon's realm. The pack features new enemies such as scorpions that shoot nails, new variants on fiends, and more.

Two new weapons make an appearance as well, a rapid fire version of the blaster weapon the Enforcer enemies use and the legendary hammer once wielded by Thor, and it will shoot lightning superior to the Lighting Gun.

The level design isn't top-notch everywhere and you can really tell that a majority of the effort was put in toward the end of the game. Some of the later levels are amazing with deathtraps and clever puzzles you will not see in other parts of quake.
The game has a start level just like Quake One where you pick your skill level (Nightmare being a hidden option as usual). You are however not given the option to pick an episode and are instead simply dumped into the game. Although it does feature three episodes, you are not really given a clear ending to each one rather instantly progressing to the next one after a brief text display.
The final boss is reminiscent of the final boss of Quake 2 (The Macron), in fact since Scourge was created first, you could argue Quake 2's was more or less a ripoff. The ending is somewhat a copout, lamely allowing you to return home 'safe and sound', it's clear these developers didn't have much in the way of an imagination nor were willing to put the time in to develop a decent story but still wanted to have one none the less.
It seems to me they went and just did what they were good at, no shame in that because what it des well, it does very well. All of scourge's levels are playable in Co-Op or Deathmatch and add a unique experience to the tried and tested Quake game.