The Miranda Blossom flower, originally appearing in Elden Ring, can be encountered as an optional boss in the open field in Elden Ring Nightreign. It can spew poisonous gas around, as well as head-butting and using its Rain of Light signature move, which covers the area around itself in beams of light.
The Miranda Bloom is accompanied by smaller Miranda Sprouts, which also attack players with their bodies and poisonous gases.
Consider fighting Miranda Blossom at level 3+.