Pope St. John I (525-526) governed the Church at the time when the Arian King Theodoric ravaged Italy. This king, having artfully enticed him to Ravenna caused him to be thrown into a dark dungeon where he died. His body was buried at Rome in the Basilica of St. Peter.
Protexisti me, Deus, a conventu malignantium, alleluja: a multitudine operantium iniquitatem, alleluja, alleluja. * Exaudi, Deus, orationem meam cum deprecor: a timore inimici eripe animam meam.
Thou hast protected me, O God, from the assembly of the malignant, alleluia: from the multitude of the workers of iniquity, alleluia, alleluia. * Hear, O God, my prayer, when I make supplication to Thee: free my soul from the fear of the enemy.
(Psalm 63:3,2 from the Introit of Mass)
O God, who givest us joy by the annual solemnity of blessed John Thy martyr and bishop, mercifully grant that we may rejoice in his protection whose birthday we celebrate.
From the Catholic Encyclopaedia: http://www.newadvent.org/cathen/08421a.htm