Abmouth Supremus is the final boss of the first dungeon you encounter in Anarchy Online. He's a ghoulish, headless behemoth with a mouth where his stomach should be and two giant flails for hands. I'm sure there's a coherent backstory that you can read as you delve into the depths of the subway that explain exactly what this atrocity is and why you have to kill it... but I definitely did not get the memo.
There is a LOT going against you in this fight if it's your first time taking him on. Anarchy Online is one of those games where how effective you are in combat is largely dependent on your buffs, how you sunk your stats, your items, and your team synergy. You don't just need gear to get ahead in AO either, you need connections because without proper buffs from high level characters, you won't be able to equip the implants and items you need to successfully solo any boss that's your level, let alone the final boss of a dungeon.
Since I was new to the game when this happened, I did not have those connections, nor the credits, or knowledge of what I should put ANY of my skill points in. I spent the majority of my time before this fight killing FLEES for XP. Yes, you read that right. Flees. Finally I was level 19 I could start wading into the tight corridors of the lower subway and slowly murdering my way to the final boss fight.
There are three key things about Anarchy Online that made this solo boss kill possible. First Dungeons are not 'instanced'. That is to say, unlike modern MMO's when you go into a dungeon, any old group could already be in there killing mobs. Mobs all respawn rather quickly so even if you cut a bloody path down the lane, it won't take long for it to fill up again.
Once I made it to the lower subs area, I discovered a group already working their way to Abmouth, and they still had an open slot. Naturally, they invited me and together we stomped through all the flees and junkies between us and our boss loot. Just four bloody froobs, having a good time.
The second thing that made my victory possible is I was playing an Agent. Agents are like Rogues from your traditional fantasy RPG, only they are even bigger assholes. You do many of the same Roguish things, but instead of having to risk getting pulled out of stealth by sneaking in close for the backstab you can just headshot someone from a across the room with a sniper rifle.
I initiated the fight. We had a Doctor, a Martial Artist, and a Tank. Their roles are not to hard to figure out. The Tank tanks, the Martial Artist is sustained DPS, the Doctor heals, and I as the Agent do burst DPS. At least that's how the roles are SUPPOSED TO GO.
Instead it was more like this.
Martial Artist: Dies
Agent: Runs away
RUN AWAY! BRAVELY RUN AWAY!
The final area you fight Abmouth (like, he has a mouth in his abs. Get it?) has a pit area, not unlike Pit in de_dust2. I ran for the pit along the edge of it and jumped up on a ledge at the back wall and... it broke Abmouth's pathing. He walked into the pit and began furiously spinning at me like a grotesque ballerina perpetually spinning on a banana peel.
So I shot him. And his health went down a sliver. So I shot him again.
Unlike modern MMO's, ammunition is a very real thing in Anarchy Online. The final reason I was able to solo Abmouth was the fact that I had something like 2000 rounds on me. I had a garbage sniper rifle. It fired about once every 6 seconds. Sometimes it missed. I don't think I came close to running out of bullets so much as hours in the day.
I might be the worst agent of all time to kill Abmoth Supremus, but I'm also probably the only player to make and enjoy a full cup of tea in the middle of the boss fight, and I'm most proud of that fact of all.