It is the true form of "Power Tool Dragon", which is shown when the Crimson Dragon releases it from its shell.
"Life Stream Dragon" appears in Yu-Gi-Oh 5D's Ending 2, and both the 4th intro and ending.
This card's attack name is "Life is Beauti-Howl" (ライフ・イズ・ビューティーホール, Raifu izu Byūtīhōru), which comes from "Life is Beautiful".
In the Japanese anime, while Summoning "Life Stream Dragon", Leo chants"The courage and power to protect the future of the planet is a revolution! Synchro Summon! Evolve, Life Stream Dragon!"' while in episode 150 Yusei and Leo chanted "To save the worlds peace, courage and strength goes revolution! Synchro Summon! Evolve, Life Stream Dragon!
This card represents Leo after he finally becomes a Signer and finds a cause by helping those he cares about (restoring Luna's and Jack Atlas's Life Points, defeating Aporia, as well as offering the card to Yusei in his duel against Z-one). This card's evolution from "Power Tool Dragon" also reflects Leo's change in personality by the second season.
This monster briefly appears in a flashback in episode 36.
In episode 142, Leo uses this card during his Ground Duel with Jack Atlas and Luna against Aporia. He Synchro Summons this card by tuning "Power Tool Dragon" with "Morphtronic Lantron". In the next episode, the third effect of "Meklord Astro Dragon Asterisk" activates, but this card's effect nullifies the damage. Leo then activates this card's first effect to make all players' Life Points that are under 2000 become 2000. This restores Luna's condition as she was slowly losing Life Points due to her body being at its last legs. This card then attacks "Asterisk" (whose ATK was 1500 due to its own effect and "Meklord Army of Wisel" being affected by the Attack Position effect of "Morphtronic Staplen"), but Aporia activates the fourth effect of "Asterisk" to send "Meklord Army of Skiel" to the Graveyard and prevent "Asterisk" from being destroyed, however Aporia still takes Battle Damage. Aporia then activates "Cursed Synchro" to prevent Synchro Monsters from attacking. When Leo sets a card, the effect of "Lock-On Laser" activates, but this card's effect nullifies the damage. Later "Red Nova Dragon" (whose ATK was 5500 due to its own effect) attacks "Asterisk", but Aporia activates "Chaos Infinity" to switch all Monsters to Attack Position and Special Summon "Meklord Army of Skiel" and "Meklord Astro Mekanikle" from his Graveyard and Deck respectively. This makes the ATK of "Asterisk" 8300. Leo then activates "Synchro Big Tornado" to decrease the ATK of "Asterisk" by this card's DEF and Luna activates "Fairy Breath" to increase this card's DEF by 3000. "Synchro Big Tornado" then decreases the ATK of "Asterisk" to 2900. "Red Nova Dragon" then destroys "Asterisk", winning Jack, Leo, and Luna the Duel.