With the magic runes tag, if I choose it for a starting weapon, can I pick any class ability or is there some limitation on choice? Also, can the one tag you get at character creation be added to abilities like Phantom Strike?
Viewing post in This World Summons Too Many Heroes!! Definitive Edition comments
For Magic Runes, the only limitation is that you cannot select abilities from the SotS classes (Sage, Magus, Champion, Servant). All other class abilities are fine!
Abilities such as Martial Art and Phantom Strike allow your limbs to be considered weapons, so they are valid choices to gain a tag at character creation.