I have come to the conclusion, at the level of opinion, that the Great Catholic Monarch is Henry V, Count of Chambord. He died in 1883, but I believe that Our Lord will raise him from the dead in His own good time. Let us pray that Our Lord will have mercy on us in this time of great evil.
The tomb of Henry V is contained in the crypt of the church of the Franciscan Monastery of Kostanjevica in Nova Gorica, Slovenia. What follows is a video of the monastery and a picture of the crypt.