With the upcoming anniversary we will get a new mechanic to enhance our favourite servants, similar to gold fous or command codes.
According to the wiki: This feature gives the opportunity to all Servants in game to enhance the base attack of their Command Cards. The UI is similar to [Command Code]Engraving, where after you have selected a Servant, you will need to select which Command Card to strengthen.
As of the update of this new feature, the Weekly Login Bonus will now include a “beast foot print” at every 7th Day of the login streak.
You can increase the attack of a command card up to 500 atk, each strengthening will give you +20 atk, so you need 25 to finish one single command card of your servant.
As far as I’m aware it is not a flat damage boost, instead it works like getting 500 additional atk from a ce for a specific face card.
Servants that will profit most from this are dps that rely primarily on their face cards, like qsh, sherlock, super orion or I guess inshun and Jekyll
But the boost is not that impactful and it will take forever to finish all face cards on a servant, you might as well give them to your favourite.