You can learn a lot about mugwort online. It is sometimes sold as a smudge bundle called black sage. Its scientific name is Artemesius vulgaris (though there may be another artemesius which is sometimes called mugwort as well).
What some people claim will help with trance work is the substance thujone. Although some people call it a hallucinogen, it is not one. It is, however, a neural stimulant. It's the same chemical which gives wormwood (another herb, known best for its use in absinthe) its properties, by the way.
The most common uses I know of are teas, smoking, and smudging. But people also use it in dream pillows, salves, and many other applications.
The smoke from mugwort can be toxic. So have ventillation, and don't 'smoke up the room.'
It will not cause hallucinations.
It will not induce trance.
But it will cause vivid dreams,
And it can, according to some, assist with more immersive experiences during astral projection, scrying, and the like.