The consistent yak card is one of the Gorajo cards a player can be given by the Gorajo hoardstalker found in the resource dungeon in Meilyr Clan district in Prifddinas, requiring level 95 Dungeoneering to enter. You can get one card per day from the hoardstalker, resetting at 00:00 UTC. This version of the card affects only the player who activated it, and there is a team version of the card that affects all of the members of a dungeon party. You can only have one solo card and one team card (of any type) at once.
To use this card, start a dungeon at Daemonheim, and click to activate it, consuming it. It guarantees that one combination potion recipe will be spawned for the player who activated the card. Note that if you already have all recipes unlocked and bought in the shop, you will not see the recipe-spawning effects of this card. The card also has a secondary effect: If the person who used the card died more than two times during the floor, the experience gained will be the same as if the player only died twice. (The Winterface will show the experience that would have been gained if the card was not used.)