Nidhogg Card

Nidhogg Card is a legendary Triple Triad card.

Source
Nidhogg Cards can be obtained as a drop in a duty or purchased from vendors.

Duties
Nidhogg Cards can be obtained as a drop from the following duties:
 * The Aery
 * The Final Steps of Faith
 * The Minstrel's Ballad: Nidhogg's Rage

Vendors
Nidhogg Cards can be obtained during the Moogle Treasure Trove event by exchanging 7 with the following vendors:
 * Itinerant Moogle