Here are some pen name suggestions based on the provided data, exploring various approaches:

Directly incorporating elements:

• Fel Antonio: Combines the nickname with a portion of the full name, maintaining a familiar feel while sounding slightly more formal.
• Baez Merced: Uses the surname, offering a sophisticated and potentially mysterious feel, suitable for fantasy.
• F. A. Baez: A more formal option using initials and surname.
• Antonio Baez: Simple, yet effective, using the middle and last name.
• Felito Merced: A blend of nickname and surname, creating a unique combination.

Fantasy-themed variations:

• Felrion: A subtle alteration of "Felito," adding a mystical "rion" suffix common in fantasy names.
• Antonio Blackwood: Combining the given name with a common fantasy surname.
• Merced the Mystic: A more descriptive pen name, hinting at the fantasy genre.
• Baelon: A shortened, more evocative version of Baez.
• Felwinter: Combining "Fel" with "winter," evoking a cold, magical feel.

Spanish/Puerto Rican inspired:

• El Fénix: "The Phoenix" in Spanish, a powerful and symbolic name.
• Mercedita: A feminine variation of Merced, adding a touch of elegance.
• Félix de la Luna: "Felix of the Moon" in Spanish, adding a romantic and mystical element.
• Antonio Sol: "Antonio Sun" in Spanish, a bright and powerful name.

Initials-based:

• FAB Merlin: Incorporating the initials with a classic fantasy name.
• FAB Rios: Using the initials and a Spanish surname.

Creative combinations:

• Baelen: A blend of Baez and Felito, creating a concise and memorable name.
• Mercedius: A slightly altered version of Merced, giving it a more unique feel.

This list provides a range of options, from simple adaptations to more creative and evocative names. The best choice will depend on the specific tone and style Felix Antonio Baez Merced wishes to project in his fantasy writing.