For my vampire hunter mod I got two things so far;

1. Leveled creature markers which spawn specialized "creatures of the night" only between the hours of 8PM and 6AM. Testing so far works well, traveling roads and wilderness is pretty safe in the daytime, travel at night is rather hairy.

2. Interior vampire NPC with an AI that wanders at night and sleeps in the daytime (open wooden coffin with a bedroll script). Vampires wander around inside small test cells at night, find a coffin in the morning and sleep until dusk unless disturbed by player.

What I'd like to do is set up a bunch of simple small crypts in assorted roadside areas with a single door for each, have the vampire(s) wake about 6 to 8 PM and leave the cell to go outside, wander in a small area then return to the cell near dawn. Studied the AI for Rhano and Varon Varmori and tried to duplicate that with an X marker, but for some wierd reason the red X was visible in game and I got a bunch of Dremora instead of a single vampire outside the cell. Optionally if it would be simpler I could have paired cells where they leave cell A, travel the road to cell B, then reverse the direction on alternate nights.

I have no idea what I'm doing here, so simple ways to do this is what I'm most interested in.

If you saw the xmarker in-game, then you must have picked the wrong thing. Xmarkers are under Worldobjects - Static. Click on something in the object window and press the X key - it should take you right to it. Drag the xmarker near your crypt and create a wander package for your vampire.

Set the AI package up something like http://www.theassimilationlab.com/forums/gallery/image/6026-ai-package/. The reference will be your xmarker. You set a radius so they wander around, near the xmarker. You can set the distance to a larger value if you want. Then create a second AI package to make them sleep in the crypt during the day. The sleep package will have a schedule. Important: make sure the sleep package is listed first in the AI package list for the NPC. The wander package should be last because that has no schedule, so it will be the default package.