A soliloquist is someone who talks to themselves, usually in a play or a story.
Being a soliloquist can make people think of being alone or of being very thoughtful.
Examples:
The soliloquist spoke to himself on the stage.
In the story, the soliloquist talked to herself a lot.
The soliloquist was very sad and talked to herself.
The soliloquist was so funny, she made everyone laugh.
The soliloquist talked to herself for hours and hours.
The soliloquist was the best part of the play because she talked to herself so much.