5,000 years ago, Life Stream served the Crimson Dragon and fought alongside him and the Signer Dragons in the ancient battle against the Earthbound Immortals. It was not present during an earlier battle against Red Nova, and instead "Black-Winged Dragon" was.
Leo believed "Power Tool Dragon" to be the Fifth Dragon, and mistakenly believed himself to be the Fifth Signer after asking Luna if "Power Tool Dragon" took part in the ancient battle between the Signer Dragons and the Earthbound Immortals. Luna replied that maybe he did, but only just to make him happy; she didn't think he was the same Dragon, since such a high-tech robotic dragon couldn't have taken part in the ancient battle. However Leo was later proven to be correct about Power Tool Dragon.
As "Power Tool Dragon", it seemed to emit, on the surface, no signs that it was anything other than a normal Synchro Monster. Individuals such as Sayer, Devack, and Lester all failed to sense any significance in it when it was Summoned. However, there were times when it seemed to show emotion when Leo was hurt.
In episode 142, in the three-on-one duel against Aporia, Life Stream Dragon finally appeared after Leo awakens as the sixth Signer. This happened as Leo asked the Crimson Dragon to lend him his power to protect Luna. He then tuned "Power Tool Dragon" with "Morphtronic Lantron" to Synchro Summon "Life Stream Dragon". During the Synchro Summon process, the Crimson Dragon appeared in order to enable Life Stream to be unlocked from its Machine form. It broke through the armor of "Power Tool Dragon", suggesting that its high-tech implants served as an outer shell and that it was not fully mechanical.