The nightshade family is diverse. It runs the course from nondescript black berries that can viciously extinguish your life, to huge, plump, near-white fruit that explode with an acidic sweetness and are incorporated into very progressive marinara.
Nightshades are all poisonous to one degree or another. Their modern descendants, the Tomato, contain the poison in their greenery, and not the fruit, though. The toxins in Belladonna and it's relatives are tropane alkaloids like atropine, scopolamine, and hyoscyamine. These toxins effect the involuntary actions of the body, and poisoning can be catastrophic. Among the most mild are pupil dilation (and it's companion, light sensitivity), but on the darker side, tachycardia (heart racing), loss of balance, rash, slurred speech, confusion, panic, convulsions, heart failure, coma and death.
Belladonna means "beautiful woman", and the deva/spirit/ally of this plant is the epitome of this archetype. She is gorgeous, luscious, tempting, and fatal. Her beauty is refined to a razor's edge, and so perfect that it is poisonous. She has turned fine features and graceful curves into pain. She is woman, weaponized.
Like any Femme Fatale, she lures you in with these looks for her own ends. Belladonna is jealous, vindictive and envious. A mask of certainty over a sea of chaos. Sampling her is opening yourself to the chaos inside.
It has become extremely trendy to take Belladonna recreationally, on the kick that "it's natural therefore safe" or for it's "witchiness". I've seen it's inclusion in incenses with no warning to keep it to the outdoors, or well vented areas. I've seen it touted for sleep (based on the film Practical Magic, I'm guessing), with no warning that an overdose means death. In short, I see a lot of people who fail to realize that gorgeous woman cannot be tamed, nor used.
Old herbals cite the use of Belldonna in plasters, poultices, and extracts applied to obscure locations such as a toenail (slower and more diffuse absorption). But never, NEVER is she taken internally. The only references I find to the internal ingestion of this Beautiful lady is by the condemned. There's sparse folklore about accused witches being slipped the poison so that they would simply fall asleep and die before they got to the gallows.
She rules death/Daath, and this connection is often viewed with a veil of childlike glitter by modern pagans. Death is the welcomed sleep, unless it comes too early, and too painfully... then it is a hateful thief. The great cycle is defined by intense joy, and intense suffering. Her realm is suffering, sad to say. From stinging nettle-thorn to bitter poison-fruit, her Apple of Sodom becomes ash in the mouth.
But... (and there's always one of those), if one wishes to explore the power of the plant, she is there to speak. You don't need to ingest it, or even touch it. A glass jar of supple, raisin-hard berries never needs to be opened to commune with her. Meditation works shockingly well to speak with her. Before I ever did any real research a nighttime chat with Horse Nettle (a nightshade relative) left me dizzied and drunk, and not in a good way. But her lessons are sharp. Visions of the gallows, of suffering, of torture, of weaponized beauty, and hateful power.