Deleted because (a) it's not passing a barrier, which the trope requires and (b) It's already on Only the Pure of Heart.
The magic sword Dyrnwyn in the Prydain Chronicles is said to only be usable by someone of Royal Blood, but it's a mistranslation and actually means "noble worth", which isn't all that clearly defined.
Deleted because (a) it's not passing a barrier, which the trope requires and (b) It's already on Only the Pure of Heart.