Much like the Dark Souls boss who can be defeated by throwing hundreds of dung pies over a wall, Elden Ring: Shadow of the Erdtree’s dual-wielding magic knight can be killed without stepping foot inside her boss room.
Several players have figured out that Rellana, Twin Moon Knight, has no answer for a Tarnished standing outside her arena and throwing magic at her until she dies. X user Ziostorm posted a video demonstrating the dishonorable act, which just involves casting long-range magic at her through a fog wall. Not just any fog wall though, it has to be the one you can only reach by going behind her home, Castle Ensis.
Quite a few spells work: Ziostorm recommends Flame of the Fell God, but other methods on YouTube use Moonveil’s ranged attack, the DLC’s Impenetrable Thorns sorcery, and even Rellana’s own Carian Sovereignty spell. As long as it’s big enough to hit her standing in the middle of the room, it’ll get the job done.
I’m not usually one to persuade anyone from cheesing a boss that’s giving them trouble, but Rellana is one of the DLC’s best fights and deserves at least a few normal attempts—if only to hear her outstanding theme. She’s a dual-wielding Carian knight who slams magical moons into the ground that you have to Mario jump over; it’s the most exhilarating duel in the game. But she can also slice you apart so fast you have no time to respond, so I understand the urge to skip her altogether.
If you must, you first have to travel south east of Castle Ensis through a ravine and fly up a couple sealed spiritsprings into the Fort of Reprimand. Once you fight your way out of there, you’ll be in Scadu Altus and can safely follow the road north to the backdoor of Castle Ensis where Rellana’s fog gate sits. Ziostorm’s clip doesn’t show Rellana trying to fight back, but she woke up and killed this player through the gate, so be careful.
I’d assume this trick won’t last very long. FromSoft is pretty diligent about fixing boss killing methods that don’t even require you to enter the room. If it does get fixed, however, you can use the route around Castle Ensis to gorge on a bunch of extra Scadutree Fragments before you fight her, which should make her considerably easier. Or you can leave the poor woman alone to mourn the utter collapse of the order she once served.