So this is a monster that was apperantly used by Yusei Fudo in an alternative timeline during the show but was never shown only briefly mentioned. Here is a comment I found on youtube that I think explains the history of the card on the anime and how it got to being made as a card:
"Cosmic Blazar Dragon is a Delta Accel Synchro monster which only exists in the anime (it's an anime-only classification). The card and monster was never shown in the entire series - only the name was mentioned. It was a veeerrrry obscure one-time mention. It was said to be the card Yusei used in an alternate future, but the card name was very faint and hard to make out. Needless to say, the Yu-Gi-Oh fandom would not let even a single small detail go by. They managed to make out the name of the card, and asked the director of the 5Ds anime himself. The director (Katsumi Ono) said that they haven't decided what to do with the card back in 2011. It was such an obscure thing after all. I bet the director just randomly made a name for the card, and he didn't actually expect people to go crazy over it. Regardless, the card is now being printed in 2017 February - a little less than 6 years after its initial mention."
With that said, here is the effect and the image:
20AP-JP051 コズミック・ブレイザー・ドラゴン Cosmic Blazar Dragon
Level 12 WIND Dragon-Type Synchro Effect Monster
ATK 4000
DEF 4000
Synchro Materials: 1 Tuner Synchro Monster + 2 or more non-Tuner Synchro Monsters
Must be Synchro Summoned, and cannot be Special Summoned by other ways.
(1) During either player’s turn, you can activate 1 of these effects.
● When your opponent activates a card or effect: You can banish this card until the End Phase; negate the activation, and if you do, destroy that card.
● When your opponent would Summon a monster(s): You can banish this card until the End Phase; negate the Summon, and if you do, destroy that monster(s).
● When an opponent’s monster declares an attack: You can banish this card until the End Phase; negate that attack, then end the Battle Phase
"Cosmic Blazar Dragon is a Delta Accel Synchro monster which only exists in the anime (it's an anime-only classification). The card and monster was never shown in the entire series - only the name was mentioned. It was a veeerrrry obscure one-time mention. It was said to be the card Yusei used in an alternate future, but the card name was very faint and hard to make out. Needless to say, the Yu-Gi-Oh fandom would not let even a single small detail go by. They managed to make out the name of the card, and asked the director of the 5Ds anime himself. The director (Katsumi Ono) said that they haven't decided what to do with the card back in 2011. It was such an obscure thing after all. I bet the director just randomly made a name for the card, and he didn't actually expect people to go crazy over it. Regardless, the card is now being printed in 2017 February - a little less than 6 years after its initial mention."
With that said, here is the effect and the image:
20AP-JP051 コズミック・ブレイザー・ドラゴン Cosmic Blazar Dragon
Level 12 WIND Dragon-Type Synchro Effect Monster
ATK 4000
DEF 4000
Synchro Materials: 1 Tuner Synchro Monster + 2 or more non-Tuner Synchro Monsters
Must be Synchro Summoned, and cannot be Special Summoned by other ways.
(1) During either player’s turn, you can activate 1 of these effects.
● When your opponent activates a card or effect: You can banish this card until the End Phase; negate the activation, and if you do, destroy that card.
● When your opponent would Summon a monster(s): You can banish this card until the End Phase; negate the Summon, and if you do, destroy that monster(s).
● When an opponent’s monster declares an attack: You can banish this card until the End Phase; negate that attack, then end the Battle Phase