"Satan entered him." It was night for Judas.
We have before us the "mysterium iniquitatis", the mystery of evil, that darkness which consumed Judas when he willed to become an agent in the rebellion of the Evil One. (Jn 13:21-33, 36-38)
Christ is "mysterium amoris", the mystery of love. When we give Him permission to enter in He makes of us agents of love and fills us with His own wonderful light.
Christ gives His saving love and puts Satan to flight through the absolution of the priest in the sacrament of Confession.