On late-night rereads of 'Re:Zero' I always get caught on how mysterious Satella really is — she's this terrifying combination of raw magical might and narrative fog. From what's shown and heavily implied, she wields almost godlike magic: vast reservoirs of mana, the ability to warp or distort reality around her presence, and curses that infect minds and hearts. The most famous thread is her connection to 'Return by Death' — the way Subaru dies and resets timelines feels tied to her influence, and many scenes suggest her power can break normal rules of life and death.
People in the world react to her smell, to her presence; characters go irrational or obsessed around her, which hints at a metaphysical charisma or a 'witch scent' that corrupts. She also appears to be able to rearrange fate to an extent, since the consequences of her interventions ripple globally in the story.
Her weaknesses are mostly narrative and mysterious: she seems bound by seals, contracts, or the consequences of her own emotions. Envy itself is portrayed as a self-defeating trait — jealousy can limit rational action — and there are hints that powerful opposing magics, certain pacts, or deep human bonds can push back. Honestly, part of what makes her so compelling is that we don’t get clean answers, and I love the slow reveal as the novels progress.