The Giant Walking Eye roams the world of Terra A.D. (or DCC), as a gigantic red thing a good 8' tall. It relays all that it sees to the rest of its body, which hides in a nearby cave. It can transmit up to 5 miles, but usually stays much closer to the rest of it.
If the Giant Walking Eye sees something that interests it, it can summon the rest of its body. If it is attacked, its body is either automatically summoned or warned, depending upon the nature of the attacker. If the attacker is weak enough to do the Giant Walking Eye no lasting harm, it is often simply consumed.
Body of the Giant Walking Eye: Init -5; Atk grasp +8 melee (2d12 plus grab) or swat +9 melee (3d12) or kick +10 melee (4d12); AC 25; HD 10d20; MV 80’; Act 2d24; SP crit as giant on 20-24; SV Fort +14, Ref -8, Will +8; AL C.
If the eye itself is an 8' tall thing, imagine the size of the creature it belongs to. Even when you take into account that the actual "eye" portion is only about 4' in diameter, and that it is a great goggly-eyed thing, the monster itself is easily over 80' tall....and that eye is really large in proportion to its body! In fact, those stats are extremely generous to the PCs who might encounter this thing. It could easily be much, much worse.
Also, it has two eyes, and the other one is probably around here somewhere.
Also, there is probably also a giant wandering nose....with a disgusting special attack!