The solution to Miranda the Blighted Bloom is to go in strong and try not to let the fight drag on any longer than needed — a somewhat discouraging strategy for builds centered around attrition, yes, but the good news is that Miranda goes down rather quickly with the right tools. Fire and slashing-type physical damage work well against it. However, you’ll want to bring at least +5 upgraded weapons in order to deal any substantial damage.
Miranda only has three major attacks: the unavoidable toxic fog, a very fast downward slam, and an AOE attack where the ground around the player shimmers before beams of light rain down to deal massive amounts of damage. These latter two attacks can’t be parried, but are easily dodged — just watch for the telegraph of Miranda rearing its head up high and jump-roll out of any sparkling around your feet.
Neutralizing Boluses or the spell Cure Poison can help with the debuff buildup. Alternatively, you can mix a Wondrous Physick with a Crimsonburst Crystal Tear for a powerful regeneration that’ll outstrip the continuous poison ticks. It’s worth noting that a well-timed whack with a torch will interrupt Miranda’s attacks, allowing you to bypass the poison entirely.
Pick your anti-poison, gear up with slashing or fire weapons, and go full Leroy Jenkins. You’ll be rewarded with a stamina-boosting amulet for your weed-whacking efforts.