Sometimes known as Clitus the Swarthy, he was a childhood friend of Alexander the Great. He and Al fought alongside each other, and Clitus saved Al's ass at the Battle of the River Granicus (in the west of modern day Turkey), by lobbing a spear into a scimitar-weilding Persian horseman who was about to embed the aforementioned scimitar into Al's skull.

Al and his band of Macedonians and Greeks were in winter quarters, having just conquered all of Persia and being right about to conquer all of western India. The Macedonians, some assorted Greeks, and some conquered Persians, Bactrians, et al. were hanging out, eating some tasty Greek fruit. Some of the Macedonians were singing songs and joking about another group of Macedonians who were beaten by a gang of Barbarians. Al thought it was great, and told them to sing some more, but Clitus protested, saying they shouldn't be making fun of Macedonians in the presence of Persians.

You have to understand that while Alexander was king, he wasn't a king like we think of kings, autocratic, throwing his weight around, beheading people because it's fun, etc. The Macedonian king was the commander of the army and that was about his only power. The Macedonians prided themselves that the king was basically just another guy like them, and they could poke fun at him and treat him like he was the drinking buddy that he was.

For the Persians, the King was the master of the universe. Everyone in Persia was literally considered the slave of the king. Alexander understood this, and he knew that that was how the Persians were used to dealing with their monarch. So when he presented himself to Persians, he did so in purple robes, had people bang their heads on the ground, and kiss his big toe.

This freaked the Macedonians out something proper, but Al actually knew what he was doing.

Where was I? Oh, yeah, a drunken Clitus was berating an equally drunken Alexander, saying he shouldn't make fun of Macedonians in front of the barbarians. Al says something the equivalent of, "Well, them dudes was pussies, and I can see you sticking up for them, you being a pussy as well." Clitus says, "Listen, dickhead, I'll have you know you'd have an axe in your skull were it not for this pussy. You're only half the man your dad was." Very bad move, Clitus. Al is quivering with rage at this point. "You'll pay for that," he says. "Oh, we've all paid enough already," Clitus says. "Having to beg the damned Persians to be able to see their own king."

Al can contain himself no more, and throws a spear at Clitus, killing him instantly. Al sobered up instantly realizing what he'd done and sobbed at the loss of his friend all night and all the next day.