Synopsis
In Silver Surfer #35 Death sent Thanos back to life with a mission, to restore the cosmic balance by killing half the life in the universe. Last issue he proposed a quicker way of achieving the aim by collecting the 6 Soul Gems. He has discovered that they each have different powers, and has renamed them the Infinity Gems. The Gem that belonged to Adam Warlock is the only 1 that is actually a Soul Gem. Last issue he took that from the In-Betweener, and gained the Power Gem from the Elder Of The Universe Champion and the Time Gem from the EOTU Gardener. But Thanos has some ulterior motive that he's hiding from Death.
1 of the Gems is in the collection of the EOTG known as the Collector. Thanos contacts him and ascertains that Elder knows what he's doing and refuses to give up his Soul Gem. But Thanos says he will bring him something very rare which he believes Taneleer Tivan will be willing to exchange the Infinity Gem for. After 'ringing off' he muses that he had better complete the deal before Collector realises what his Gem can do or the Elder will be able to kill him.
So the Titan sets of in his teleporting chair/throne in search of another Elder the Runner. But when he reaches his target's location his chair is whittled away by the speeding Runner, who says that another Elder Grandmaster warned him that Thanos would be after his purple Gem - a Gem which has upped his already-phenomenal speed to instantaneous travel. There then follows a game of tag where all Thanos' eye-blasts miss the racing Elder and Runner continues to break up the chair until the Titan is left clinging to a fragment.
Then Runner stops and asks Thanos why he wants the Soul Gems. The Titan willingly explains that in Death's Infinity Well he learned the truth about them. In the beginning there was only 1 being in the whole of reality. Despite his limitless power his lone existence became unbearable and he committed suicide. But from his death arose the universe, and the core of his being survived in the 6 Infinity Gems. With such power Thanos could sit at Death's side as her equal.
Runner thanks him for the info and says he'll kill him now. But Thanos stops pretending to cling to the chair-bit and faces his foe with confidence. He explains that Runner's Gem didn't actually make him faster. It is the Space Gem and gave him a subconscious teleportation ability. But Thanos has the Time Gem and he's been using it to age the Runner, who is now a million years old and can't fight back as the Titan takes his Gem.
Then Thanos moves to stage 2 of his current plan. He de-ages the golden Runner to a little baby. And then, using the Space Gem in place of his ruined tele-chair, he teleports them both to the Collector's space ark. And there he offers the baby Elder in exchange for Collector's Gem. Tivan doesn't know why Thanos wants it because it doesn't do anything, but agrees to the swap as long as it includes a promise from the Titan to leave him alone in future. Thanos agrees to that ...
... but after the exchange he reveals what his new Infinity Gem can actually do. It is the yellow Reality Gem and he uses it to alter the surroundings in mind-bending ways. But before going after the last Gem, in the possession of the EOTG Grandmaster, he lets Taneleer know that the change to Runner was only temporary. And the other Elder reverts to his normal adult form and starts beating up his 'brother' who was going to keep him in his collection. Much to the enjoyment of other caged specimens.
Grandmaster has been watching the proceedings remotely, and now he awaits the arrival of the Titan. Thanos teleports in and En Dwi Gast explains the rules of the game they will play. The Gem is held in a pan-dimensional teleporter. Any attempt to break in to it will cause it to send the Gem to a random unknown location and then self-destruct so that location can't be traced. It will do the same if GM is killed. But if he loses the game then the PDT will shut down, releasing the Gem. The game itself will take place on the mental plane. They will have identical armour and weapon, and a 'killshot' will immobilise the loser and end the game. Gast asks Thanos to wager the other 5 Soul Gems in return. Thanos agrees and places them in a stasis field that will deactivate if *he* loses, which he doesn't intend to do.
They don headsets which take them to an abstract plane like a huge chessboard with blocky obstacles. Thanos senses that GM lied and a killshot will actually kill him. There ensues a cat and mouse game of blasts and dodging. Gast's knowledge of the terrain gives him an advantage. But the Titan changes the rules by blasting a hole in 1 of the obstacles and hiding in it and catching his opponent unawares. But when he takes the killshot his weapon backfires on him and, as Grandmaster explains, he's encased in a silicon-based fungous that will permeate his entire being within moments.
En Dwi Gast then explains further that he had begun to suspect the true power of the Gems, and as he watched Thanos defeat the other holders he learned much more about them. He allowed the Titan to collect the others so that he himself could win all 6 in this game. But them he taps the solidified fungus and it falls apart to expose not flesh and bone but metallic parts (obviously a robot capable of entering the mental plane). And the game reality crumbles around him ...
... as the real Thanos smashes the game controller. GM's body is comatose and the Titan takes the blue Mind Gem. He muses that if the Elder hadn't been so sure of his gaming abilities he might have worn the Mind Gem and discovered his opponent was a robot duplicate.
Now he gloats that he has all 6 Infinity Gems that will give him even more power than the Cosmic Cube (in the Thanos War mainly in Captain Marvel #25-33). With the Space and Time Gems he can travel throughout space-time. With the Mind Gem he can read and control minds. The Power Gem powers the other 5. The Soul Gem allows him to mould the essence of anything living or dead. And with the Reality Gem he can remake reality as he wishes.
And what he wishes most is to be at the side of his love Death. And so he immediately appears before her throne and her servants Ratter and the spokescorpse. The corpse tells him that Death knows what he has become, and Thanos tells her that he did it for her. He wasn't content to love her as a thrall, he wanted to be her equal and consort. Death transforms her head from a skull to a human female, and she creates a throne beside hers. The corpse says that his wish is her command. He ascends the throne and says they will spend an eternity of bliss together. This time it is Ratter who repeats that all will be as he wishes.
Thanos at last senses that something is wrong. Why will Death still not talk to him directly? Ratter explains that Thanos is *not* her equal, he is far above her and it would be unseemly for even Death to address him directly. As the Titan realises the truth he takes his anger out by causing Ratter to explode. Then he walks away because in winning supreme power he has lost what he most desired.