The Blue Fast is a blue mob resembling a player without a head, it runs at the speed of a player under the speed II effect in one direction until it despawns. It has only 1 health point, but remains a neutral mob, and if hit with a snowball or egg it will charge the player and do 3 damage upon hitting them.
Upon death, it stops moving forward, but continues to play its running animation, before exploding, dropping a Blue chisel.
Blue Fasts share their running and being damaged sounds with the player, but have a trumpet upon death.
Red Fasts are red versions of Blue fasts, they run in zig-zag patterns and occasionally change direction, spreading fire as they run. Red Fasts can only be created if a Blue Fast is hit by a Molten Tear.