Reached through UPDATES. Deadly both ways. It runs straight along U or V at two to five units a turn, flipping between two graphics as it goes, for a random number of turns up to 15 (none left counts as 256); when it is stopped, is blocked, or has run its turns it beeps and turns a quarter, left or right at random, with a new speed and a new count.

The way it faces is its mirror flag (bit 6 of +7: clear along U, set along V) and bit 1 of its graphic (which way along it); a turn always flips the mirror flag, so always changes the axis, and flips bit 1 or not by the random number. The speed is the turn counter's low two bits plus two. +10 counts the turns left. Rooms $3F, $42, $45, $4D, $72, $A9 and $D8 have them (object template 28).