ToME: the Tales of Maj'Eyal

I'd like to make a new particle effect for Mosaic but I have no idea how to go about it... I'd like to leave a little trail behind the player as he moves, which may disappear under certain circumstances. The trail would be a line from the middle of one tile to the next, looking like a bolt of lightning, but with a little bit of animation to it. So essentially a simple line that can be turned on and off.

Er, any clues on where to start? I'm not aware of anything similar in ToME (my usual source of particle effects).