Creepy Things in the Sewers, Part 1 (maps and prep)

July 26th was supposed to be the next meeting of our full group. I was all set to run Treasure of Talon Pass, which I picked up at Free RPG Day a few weeks ago. I spent hours prepping battle maps, pulling minis, and printing copies of stat blocks so I could run the entire adventure without cracking a core book.

So, of course, I had a player cancel with two hours' notice. It was time to put the much-lauded quick adventure prep abilities of 4e to the test for the reduced group.

Fortunately, I already had a general idea of where the smaller group's next adventure would take place. I had come across a two-sided battle map from an early-3e-era Dragon magazine with a village square on one side and some twisty sewer passages on the other. I had a general idea that the gnomes they fought in the library were going to have friends, and they were all involved in some twisted scheme. This scheme would of course be bad for the town the PCs were in (the one they had saved from the plague in their first adventure).

So, with maps in hand I cracked the DMG to see what it would tell me about constructing a complete adventure from scratch. Hello, page 104:

On average, it takes a character eight to ten encounters to gain a level, with the possible addition of a major quest. For a group of nine encounters, here’s how they might be broken down.

This is followed by a very handy table. For 4 2nd level PCs, that table coupled with the target xp table on page 57 resulted in:
400 xp - 1 encounter
500 xp - 3 encounters, 1 quest
600 xp - 3 encounters
800 xp - 1 encounter

I wanted to throw in a skill challenge, but I didn't think I had time to come up with one. I then went to the Monsters By Level table in the back of the Monster Manual. I simply started jotting down the monsters that didn't appear in Talon Pass so I could try out running as many different monsters as possible. A sample of the encounters I came up with:

1 adult kruthik, 1 young kruthik, 3 hatchling kruthiks – 393 xp total
2 ochre jellies – 600 xp total
2 rat swarms, 2 dire rats, 2 giant rats – 500 xp total

It took a few minutes to figure out what these monsters were doing in the sewers, and a few more to scatter them around the maps I had. Maybe 15 minutes to pull minis. Finally, I copied, organized, and printed off stat blocks for all the monsters and wrote in each one's starting hit points for tracking later.

Analysis:
All told, it took 1.5-2 hours prep time to drive a 4-hour session, and I had encounters to spare (which are scheduled to be played through tomorrow). Given more time, I probably would have tweaked the level down on a tiefling heretic to replace or support my BBEG. I guess since they didn't reach that encounter I still have the option...