The Man-Beast had kidnapped four members of the Infinity Watch and was holding them unconscious in a stasis tank, in his ship high above the Earth. Man-Beast decided to 'safely' draw power from the Infinity Gems through a computer system of his, rather than directly. He used this "Instrumentality" to avoid becoming intoxicated with the power of the Infinity Gems as Thanos previously had. Warlock came to rescue his captured teammates, and succeeded in defeating the Man-Beast's soldiers and Triax the Terrible. When Warlock confronted the Man-Beast, Man-Beast used his "Instrumentality" to create the Infinity Thrall and sent it to kill Warlock.
This resulted in arguably one of the most impressive cosmic battle-issues of all time, as Warlock tried desperately to stay alive while being hunted by the truly unstoppable and invincible killing machine. Warlock eventually comes up with a plan, luring the mindless Thrall into destroying the Man-Beast ship's engines and generators, depowering the machinery that was creating the Thrall, and destroying half the ship. The Thrall vanishes after destroying its own power source.
The Infinity Thrall has the full power of at least four Infinity Gems, minus the Soul Gem (and possibly the Reality Gem) - this makes it a colossal cosmic monster with near-unlimited power, it was dependent upon a star-ship powered engine to manifest in the physical universe, however, if this engine was destroyed the energy-being would disperse : being an energy-construct the Infinity Thrall is also immortal and could return at any point, if anyone ever managed to recreate the Man-Beast's machine.