Hulk has an untimely brush with an associate of Xemnu's - Diablo!
Story takes places this between Hulk #198-199.
The living Titan known as Xemnu operates from within a secret laboratory beneath a lake in Colorado. Sensing the presence of the incredible Hulk nearby, he creates simulacrums of five powerful beings that once threatened the Earth and sends them to defeat the Hulk.
The Hulk meanwhile, wandering through the forests accidentally trespasses onto a U.S. Army proving ground. He fights through a squadron of soldiers before coming face to face with the first of Xemnu's minions - Diablo! Hulk struggles with Diablo, but manages to disperse his smoke-like form with one of his patented power-claps. The battle however, leaves the Hulk physically drained.
The next creature the Hulk fights is the muck-monster, Taboo. The two fight in a deep riverbed. The Hulk anchors himself to the silt, then creates a massive whirlpool that pulls Taboo down until his body discorporates. Once again, the Hulk is uncharacteristically fatigued from the fight.
Immediately following this debacle, the Hulk encounters Groot - the Monster of Planet X. Groot tries to kill the Hulk by firing wooden needles from his fingertips, but the Hulk pulverizes him with two broken chunks of rock.
Following this, he then battle Goom. Goom uses his molecular condensor beams to shrink the Hulk in size, but the Hulk still manages to defeat him. He batters him into a mountainside causing a rock slide that buries his opponent. When the battle concludes, the Hulk returns to his normal size.
After this the Hulk comes face to face with the electrical being known as Blip (whom the Hulk confuses with Zzzax). Blip electrocutes the Hulk with over a million megavolts of electricity, but the Hulk shorts Blip out by heaving him into a set of power lines.
Having witnessed the failure of all of his agents, Xemnu finally decides to confront the Hulk personally. He abducts him and brings him to his underwater base. He reveals to him that his artificial monsters were designed to rob the Hulk of his strength. The Hulk breaks free and charges at Xemnu. Xemnu gets inside an escape bubble and leaves the base. The Hulk grabs a hold of the strange vessel and rides it to the surface of the lake. The two titans continue fighting one another atop a dam. Their blows cause the dam to collapse and they are both swept away in a flooding rush of water. When the Hulk gathers his senses, he discovers that Xemnu is gone. Irritated beyond measure, the Hulk leaps away, hoping to find some peace.