I noticed there wasn't a Gerald Brom lora for SDXL. There is now, just in time for Halloween. Enjoy. Include "in the style of Gerald Brom", "dark fantasy" for best effect.
Recommended strength: 0.5-0.7. Keywords you can use to push it in a direction (though not required): Undead, Warrior, Sorcerer, Gunslinger, Angel, Demon, Fleshcraft.
To remove watermarks, lower the strength of the lora to 0.5-0.7 and put (Signature:1.5) and (Watermark:1.5) in the negative prompts. Or, for more authentic BROM, allow the BROM to appear in your images.