I dunno if that illustration has anything to do with Erac's Cousin, but I sure would like to think so.
From the Rogue's Gallery:
Erac was a lawful good wizard who reached the level of Warlock (6th level) adventuring in and around the ruins of Greyhawk Castle. On one expedition into the dungeons below the castle, while exploring the sixth dungeon level, he discovered a small sublevel separated from the main dungeon by a single corridor. At the end of the corridor, Erac discovered a small area containing many small, shallow wading pools, the ceiling overhead was decorated to look like a star-filled night sky. Upon entering the area, a wall slammed shut behind him, cutting him off from the main dungeon and trapping him in the newly discovered sublevel. Erac never discover the secret for escaping his prison, and eventually he succumbed to starvation.
Several months later a wizard that refused to divulge his name, but claiming to be Erac's Cousin, began adventuring in the Greyhawk Dungeons. Erac‘s Cousin, as he came to be known, discovered Erac's remains. He also discovered the secret of escaping from the dungeon. The magic words needed to escape were hidden among the stars on the ceiling. Erac’s Cousin owed much of his early success to the Wand of Fear and the Silver Horn of Valhalla that he recovered from Erac's body.
Erac’s Cousin has never revealed his true name for he reckoned there was power in knowing another's name.
Erac's Cousin was lawful good, but he was also greedy, a trait that the wizard Bombadil was able to use to his advantage. Deep in the dungeons of Greyhawk Castle there stands an enormous stone statue known as The Great Stone Face, or The Enigma of Greyhawk. A ring of strange runes circle the base of the statue, and the statue itself radiates magic. Many adventurers have tried in vain to unlock the enigma's secrets. While adventuring alone in the dungeons Bombadil placed a Magic Mouth spell on the stone face that when triggered stated, "The ways of balance need to be maintained. Give your most prized possession as a gift freely to one who walks the path of balance and your great reward will follow in short time." Shortly thereafter Bombadil returned to the chamber of The Great Stone Face, this time accompanied by Erac's Cousin. While exploring the area Bombadil conveniently placed himself out of hearing range of the spell. As planned his unnamed companion triggered the spell, and a short time later donated a potent magic item to the sly Bombadil, who just happened to be the first neutral character Erac‘s cousin ran into..
One of Erac's Cousin's more memorable adventures occurred after he spotted a strange red star in the night sky. He drifted off to sleep thinking of the strange star and when he awoke he discovered he had been transported to Mars. To his surprise he arrived stark naked. Soon after his arrival, the mage was attacked by the Cannibals of Ugor. Much to his dismay, he discovered that magic didn’t work there, and he was forced to fight toe-to-toe with the bloodthirsty cannibals using nothing more than a tree branch. In time the unnamed adventurer adapted and ultimately excelled in is new environment. Due to the planet's low gravity the marooned wizard's strength was heroic. He could leap 20 to 40 feet into the air, and much further than that forward. During the many months that he spent there, being unable to use magic, Erac's Cousin began training as a fighter. Instead of using magic to defeat his enemies, he would now cut them down with a sword. Before returning to Oerth he had slaughtered hoards of Green Martians, and organized an escape from the mines of the Yellow Martians. Finally he discovered a method of returning to Greyhawk. He found Oerth in the night sky before going to sleep and when he awoke he was back home. Unfortunately his arrival home was similar to his arrival on Mars; naked. He had left a fortune behind on the red planet.
As Erac's Cousin grew in strength a rivalry developed between him and some of the other powerful characters of the World of Greyhawk, particularly Lord Robilar, who successfully managed to persuade several of the unnamed wizard's henchmen to desert their master and follow him. Erac's Cousin was quite powerful, but remained reluctant to confront the powerful warrior. Robilar was always in the back of the mage's mind and he was always sure to have a number of area effect spells memorized to counter the fighter’s Ring of Spell Turning, and a Dimension Door ready in case a hasty retreat was called for.
Already a powerful wizard and a capable fighter, Erac's Cousin became even deadlier after he was transported to Wonderland through a gate in the Greyhawk dungeons. While traveling across the bizarre demi-plane he ran into Tweedle Dee and Tweedle Dum. The twin brothers offered him some silly looking trinket they had in exchange for a wand he was carrying. When he returned to the Greyhawk dungeons the trinket transformed into a Vorpal Blade. Later he acquired a second Vorpal Blade as part of a treasure he discovered while adventuring in the wilderness. The swords were both holy swords that had additional powers that would only work for a paladin, but the greedy adventurer was never willing to part with either of his prized weapons. In combat he would summon monsters, cast a few damage causing spells like Magic Missile and Cone of Cold and then go charging into battle wielding his two powerful magic swords.
Back in the Greyhawk dungeons, Erac's Cousin and the fighter Ayelerarch came upon a beautiful face that cried golden tears. The face told the adventurers the tale of his imprisonment and the heroic deeds required to release him. The adventurers agreed to recover The Urn of Moon Dust from a group of werebears. Erac’s Cousin and Ayelerach successfully recovered the urn, and to complete the quest, they sprinkled the moon dust on the weeping visage. The face was actually the demon prince of deception, Fraz-Urb'luu, who had been imprisoned by the mad arch-mage Zagyg centuries earlier. The completion of the quest resulted in his release. When he came to his proper form the adventurers attacked the fiend to try to undo their foolishness. The enraged demon fought back fiercely. In desperation Erac's Cousin used a gate spell from a scroll he had and managed to gate in the god Zeus, but to their shock and horror, the god chose to ignore their plea for help. The demon then whisked himself and the adventurers back to his own plane where strange forces there drained the magic from all the items Ayelerach and Erac's Cousin were carrying, including Erac's Cousin's prized Vorpal Blades. Fraz-Urb'luu quickly subdued the stranded adventurers and they suffered unspeakable tortures at his hands before they eventually managed to escape.
Erac's Cousin blamed the gods for the suffering he had endured at the demon’s hands, and for the loss of his prized items. He bitterly turned his back on the good powers he had paid homage to in the past, and instead chose for himself a path of evil. The unnamed wizard called upon the archfiend of Hell, Asmodeus, and a pact was made. The one-time powerful force for good, was now one of Hell’s greatest champions. To aid in his endeavors, and as part of their pact, Erac's Cousin was given an imp as a familiar. He does not trust the imp though, and he fears Asmodeus may have deceived him somehow.
From this point on, Erac’s Cousin became a psychotic killer. He quickly slaughtered all of his former associates and henchmen, stole all of their wealth and magic, burned down his stronghold, and became a wanderer, traveling only with the imp, in rat form, for a companion.
Erac's Cousin has taken several longevity potions and seems very young. He is able and deadly, but also paranoid, and he avoids any situation he finds risky.
Since the unnamed spellcaster first discovered Erac's body, he has kept it in his possession. Originally he kept the body hidden in a secret location, but now he carries it with him, keeping it stashed in his Portable Hole. Occasionally Erac's Cousin still thinks about resurrecting Erac.