Feels a bit unfinished, but WIP as you said. A few things came to mind.
What do the aliens look like? Classic aliens, space dwarves, Marvin, the Martian? I don't know what color they are, and the description is very vague. I would request more details about their appearance.
What do their ships look like. What shape, what color, is their mode of propulsion visible, ala engine glow, or do they have reactionless drives? At first, the comet mistake is fine, they are a very long way from Earth's observation, and the things out in the solar system that can see them are likely old, having been launched years before.
Minor detail: the B3 controllers on Earth aren't going to be able to respond to what happens on Mars because there is a lag between Earth and Mars, the images the rover sends back are several minutes old by the time they are viewed, likewise, the signal telling the rover to move will take several minutes to arrive. Go to Comment
All the math on this one should be done by the DM. Let the wielder suffer for a little as he rolls a 19, misses, and his thief friend rolls a 17 or something and hits. Isn't messing with players fun? Go to Comment
Maybe a person starts off using this sword (knowing nothing about it, of course), and quickly gains a reputation as a great swordsman (due to the sword.) Imagine their surprise when they use another sword and discover that they use another sword and discover that they're really extremely bad. Go to Comment
For all it's simplicity, I actually think this is great, and could easily be added into a game to confound a player who is getting a little bit too big for his britches. Strolen's thought of having the GM do the rolls and keeping the stats a secret is a great idea! Go to Comment
There's always the age-old possibility that the sprite was confined for a good reason and that letting him out will have bad consequences: maybe he was a thief or murderer. Maybe the sprite is a carnivorous scavenger and wants the mage to fall into the gorge and die providing him with a tasty meal. Go to Comment
Back to the plot!
Combine that comment above with another plot on this page...
After freeing the spirit it will be so thankful that it becomes the mages unwanted companion, helping where it can (thievery included). Solve this. Go to Comment
What exactly was the lesson the sprite was supposed to learn? Also, consider the possibility that the sprite can't read, or at least can't read the scrolls the mage had. The sprite could become a companion, at least for the trip to the bottom of the gorge, for some time.
What killed the mage? Yes, there's undead at the bottom of the gorge, but are they really so powerful or numerous to have overwhelmed the mage? There could be a more nefarious force that killed the mage - A magic poor area. The victim mage blundered into the undead and tryed to use his spells to destroy them, only to find his magic unavailable. Even simple skeletons and zombies could overpower a magicless mage. Go to Comment