Yeah, I know. What's so funny about a bunch of recently captured cities? Well, I'll tell you. All of those cities(except the one in the north with 1 pop, I just founded that one) were captured in under 15 turns - and they were all captured by a single unit.
It started off with a ship wreck. On this whole little island I'm on, there was one ship wreck. It was in Sandalphon's territory, so I couldn't get to it earlier, but when he declared war on me I sent a galley north to explore it. The result was an assassin that was trapped in the lair. Given I wasn't even close to building my own assassins, I was pleased with the result, and also very cautious of using him. However, I slowly picked off the weaker units Sandalphon sent into my territory(his military was vastly superior to mine at the time, and I had to turtle in my cities) Over time, my Assassin got several useful promotions: Drill IV and Combat II.
Then, the real gamechanger happened: My Assassin was chosen by Aeron. With 2 more strength, he became a killing machine, and after I got Blitz he singlehandedly killed all of the units Sandalphon sent at me. For a while this continued, with Sandalphon sending units at me, my assassin killing them, until I noticed something: My assassin had 97.3% odds(with 2.3% withdraw chance) attacking the units in his cities. So I started attacking them, mainly to give my unit more experience, but before I knew it,
I was actually conquering his cities. With an assassin. From the time I captured the first, I captured the rest in only 13 turns, with only one unit.
Look at his promotions in the screenshot, and check in EXP
EDIT: My assassin just assassinated Hyborem!
This is what happened. Two turns after I took and posted this screenshot, Hyborem entered into the world. Dis was created three tiles to the north and one tile to the east of Borlans(my northernmost city in the screenshot). Immediately after he spawned, I declared war on him(I sure as hell wasn't going to share my frozen tundra with no commercial or agricultural value with him!), moving my assassin east to kill a Champion and Longbow he was using to escort a settler to found his second city. Hyborem and one of his Champions attacked and captured Borlans, which was undefended at the time. The next turn, I had my Assassin attack and kill the Champion in Borlans. Then I cast Raging Seas to weaken Hyborem, and took the Shock promotion on my Assassin(I was saving that for Subdue Beast, but this was so worth it), moving my combat odds from 14% up to 92%. Then I attacked and killed Hyborem the first time. Since he is immortal, he respawned in Dis, but being an assassin and all... the following turn I moved my Assassin over to Dis, attacked Hyborem, and killed him for good. Now I'm using my assassin to mop up the rest of his units!
That settles it. I must write a RP story about this.