A young man stands against a deep, dark background, his pale face framed by curling brown hair and illuminated by a cool, almost spectral light. He gazes slightly to his left, his large eyes set in a face marked by sharp features and a thoughtful, distant expression. His right hand is raised in a gentle, open gesture, palm turned upward and fingers elegantly extended, while his left hand firmly holds a golden chalice.

The figure is draped in voluminous robes: a vivid green mantle covers his left shoulder and arm, while a white garment tinged with pinkish-purple shadows sweeps across his chest and right arm. The folds of the fabric are painted with broad, energetic brushstrokes, creating a sense of movement and depth, and the play of light across the surfaces gives the cloth a luminous, almost otherworldly quality. The background is a featureless expanse of darkness, which serves to isolate the figure and heighten the dramatic contrast between the illuminated face, hands, and garments and the surrounding void.

The gold of the chalice is rendered with careful highlights and shadow, suggesting its weight and preciousness, while the dragon's form is painted with quick, expressive strokes that emphasize its fantastical nature. The composition is tightly focused on the saint, with his upper body filling the frame and his gestures guiding attention to the symbolic chalice. El Greco creates a sense of spiritual intensity through the elongated proportions of the figure and the striking color contrasts. The work is part of the Mannerism movement, characterized by its expressive forms, vivid colors, and dramatic presentation.