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.
With Rashomon Event Rerun updates, It is now possible to add 4★ cards to servants. but it can only be fed to servants that already maxed their original status (1,000). while 1-3★ will have no effect when fed from 1,000 status and above.
Status Up Cards can be acquired in the Friend Point Gacha or bought with Mana Prisms. Permanent stat increases granted by Status Up Cards are capped at 2000 for each stat.
1★ cards will increase one stat by 10, 2★ cards will increase it by 20, 3★ cards will increase it by 50 and 4★ will increase by 20.