Before becoming the Cosmo Pluck, the device took the form of the Pyroxene stone (Cosmo Stone), a stone given to Musashi when he was a child by the blue giant himself. The purpose of the stone was the same as the Ultra Star stone seen in Ultraman Tiga, to summon its Ultra owner from whatever part of the universe.
Musashi kept it as a child and as he grew up taking care of tame monsters he used it to bond and calm down the monster Lidorias. When she was taken over by the Chaos Header Virus, Musashi tried to use it to calm her down and initially succeeded but she was attacked by the SHARKS and reverted to her mutated state. Musashi's plane was shot down, but Cosmos, sensing the danger swooped down from space and merged with him.
After Musashi showed his resolve to save the monsters, the stone morphed into the Cosmo Pluck allowing him to transform at will (so long as Cosmos allows it).
When it was still the gem, when Musashi first summoned Cosmos, he was shown like blooming from a flower then Cosmos just stands up. When it was already the Cosmo Pluck, Musashi raises the Cosmo Pluck and shouts "Cosmos!" and a flash of light envelops Musashi and transforms him into Cosmos's default form of Luna mode. At times Musashi has just used it in a similar fashion to the Beta Capsule without shouting. Other times Musashi has transformed without saying a word but the word Cosmos could still be heard, implying he was saying it in his mind or it was there to be cinematic.
|Showa Items||Beta Capsule | Ultra Eye | Willpower | Ultra Rings | Ultra Badge | Leo Ring | Beam Flasher | Bright Stick | Bright Bracelet|
|Heisei Items||Delta-Plasma | Willpower | Beta Capsule/Flash Prism | Estraller | Pikari Brusher | Spark Lens | Reflasher | Esplender | Agulater | Nice Dreamer | Cosmo Pluck | Just Lancer | Evoltruster | Darkevolver | Max Spark | Mebius Brace | Knight Brace | Ultra Zero Eye | Saga Brace | Ginga Spark | Dark Spark | Dark Dummy Spark | Gunpad | Ginga Light Spark | Livepad | Victory Lancer | Chibull Spark | Ultra Fusion Brace | X Devizer | Orb Ring | Orbcalibur | Riser | Ultra Zero Eye NEO | Giga Finalizer | Gyro | Orb Ring NEO|
|Reiwa Items||Taiga Spark | Tregear Eye | Taiga Tri Blade | New Generation Eye | Z Riser|
|Other Media Items||Zoffy Bracelet | Jack Bracelet | Gorian Belt | Zaji Sword | Drew Bracelet | Flare Coin | Alphone Pendant | Ars Ring | Mimicry System | Ultra Operation|