In true FromSoftware fashion, Elden Ring Nightreign features a challenging boss battle against a familiar face from the original game in the tutorial that is meant to be lost, which delivers a straightforward message: the game is challenging. While this first fight against the Fell Omen can be difficult, it can be won using a relatively simple strategy, and you will also get a nice reward for your effort.
As the tutorial features a set number of enemies and specific equipment, putting together a winning strategy is much easier than in the actual Elden Ring Nightreign experience. Make sure to defeat every enemy you encounter as you proceed and open every treasure chest. By doing so, you can get to level 6 and have the Cold Katar and Rogier’s Rapier Armaments in your possession. Equip both of them to use the powerful Hoarfrost Stump skill and activate the Multiple Periodical Glintblades passive.
With these Armaments equipped, head over to the ruins where the Fell Omen awaits, bring the Duchess back to life as prompted, and wait for the enemy to appear. When it does, keep your distance, let the Duchess hold his attention, and use Hoarfrost Stump or attack repeatedly with the Cold Katar after he uses any hammer attacks to inflict frostbite. Once you have accomplished this, keep your distance and attack only after the boss uses hammer attacks, letting the Continual Glintblades deal some nice burst damage without doing anything else. If the Duchess dies, use the Wylder’s Ultimate Art to bring her back instantly. Try as much as you can to defeat the boss without dying, as you won’t have the Duchess’ help during your second and final try, making everything much more challenging.

After defeating the Fell Omen, sit in the chair to end the tutorial and begin the proper Elden Ring Nightreign experience. As you awaken in the Roundtable Hold, you will be informed of having been gifted the Fell Omen Fetish relic, which boosts your attack power when you switch weapons, improves throwing knife damage, and increases Vigor by 1. If you have not defeated the Fell Omen on your first try, you can replay through the tutorial by accessing the Visual Codex, selecting Guide, and pressing the Square/ X button.