všickni páni, co je královic vysvobodil...


Gramatika: co indicates that the clause modifies the immediately preceding noun (páni); co does not decline. In most cases, when the function within the relative clause (in this case acc. because it’s the direct object of vysvobodil) is either nom. or acc., co is not followed by a pronoun. Here, however, we see acc. pronominal form je following co.