Beholders

Large eye shaped createres noted for their notoriously bad tempers caused by the inability of alchemists to find a potion that can relieve any of their itchy eyes.
First time space travllers often make the mistake of laughing at them when they first encounter one. Depending on the mood of the beholder, the unfortunate traveller either gains a new best friend or ends up as a pile of dust. Avoid if at all possible.