Link-strike

Link-strikes and blindside-strikes  are co-op attacks the player can perform with party members and their Level 10 chocobo in Final Fantasy XV.

Mechanics
The player can perform link-strikes with the three default party members, Gladiolus, Ignis and Prompto, but also with guest party members. Linked attacks can trigger when blindside-attacking an enemy, or when parrying an enemy attack. Link-strikes can be performed with a party member nearby who isn't incapacitated by a status ailment or in Danger. Link-strikes can be initiated when Noctis wields a sword, greatsword, or a lance; royal arms never trigger link-strikes.

Once a link-strike initiates they cannot be halted and the participants cannot be hit for its duration. The Friendship Band accessory allows link-strikes to initiate even across a distance. It is often the easiest to trigger link-strikes with Ignis because his AI behavior has him stay closest to Noctis. He also has the most powerful link-strike if Noctis strikes an enemy from behind with a greatsword.

The Critical Link Ascension ability makes all link-strikes critical hits. Limitless Link allows link-strikes to break the damage limit, and Link Up boosts link-strike damage. Super Link Up further boosts link-strike damage.

Performing a blindside-link the first time earns the Blind Spot achievement/trophy. Initiating a link-strike after parrying yields Noct You Like a Hurricane.

Final Fantasy XV: Episode Gladiolus
Gladiolus can perform link-strikes with Cor Leonis. Doing it five times earns the Master and Pupil achievement/trophy.

Final Fantasy XV: Episode Prompto
The player can perform link-strikes with Aranea Highwind. The Beauty of Teamwork Archive Highlight is obtained on the bridge in the room before the Barbarus corridor when the player performs a link-strike.

Final Fantasy XV: Episode Ignis
Ignis can perform link-strikes with Ravus Nox Fleuret.

Final Fantasy XV: Assassin's Festival
Noctis and Prompto can perform a blindside-link against a cactuar in Whack-a-Cactuar 2. Doing this to the Gigantuar nets 4,000 points.

Trivia

 * Cor and Iris share a link-strike of a high spinning kick.