Status Up Cards are 1★ to 3★ cards that increase a Servant's HP or ATK stat permanently, turning the increased stat yellow. The current amount of Status Up Cards on a Servant can be seen just below their HP & ATK stats at the Servant Status screen.
1★ cards will increase one stat by 10, 2★ cards will increase it by 20 and 3★ cards will increase it by 50.
There are Status Up Cards for every class except for Shielder, Ruler, and Avenger. Status Up Cards purchased with Mana Prisms are not class-restricted.
They are used in the same way as Experience Cards, but will give the servant 12 experience each.