|This article, Bliss, contains spoilers. Be forewarned, plot and/or ending details follow.
She is a 'young woman' introduced as the Gaian constituent who first greets Golan Trevize and Janov Pelorat, who are on a mission to find Earth. What they find is Gaia, a planet that is one large organism where every person, every tree, every sandgrain is part of the organism, sharing group memories. Bliss, like all Gaians, has two natures: her private role as Bliss, and her meta-role as being a constituent element of Gaia. She often says "I/We/Gaia" to make clear that she is speaking of the whole of Gaia as a superorganism.
Bliss joins Trevize and Pelorat on their journey. She and Pelorat fall in love, despite their age difference. Trevize dislikes Bliss' nature at first, and suspects her of being a robot, but eventually they become friends and work together.