The use of these marks is more similar to runes than one would expect though.
Basically, each character comes with a preset inventory of marks that you gain as you progress through the plot. (So, no secret overpowered marks to be obtained!) And, each character has four "slots" to equip these marks.
A mark may contain either a boost to specific stats (see: skills or status runes), powered up physical attack commands (see: command runes) or specific magic spells (see: more like single-spell scrolls as opposed to magic runes).
In other words, the introduction of these Marks of the Stars pretty much supersedes the Runes system from past titles. At least, as far as Tierkreis and its spin-off status is concerned.