Kelsier is a half-blood skaa Mistborn and brother of Marsh. He is described as smiling often and easily, a small act of rebellion against the Lord Ruler’s oppression. Kelsier is confident, skilled in Allomancy, and works only with skaa thieves that he can trust. At the beginning of Mistborn, Kelsier has a deep hatred for the nobility because his skaa mother was killed by them. Eventually, Kelsier’s hatred for the nobility lessens thanks to Vin’s influence and her love for Elend Venture.

Prior to the events of the novel, Kelsier was a well-known and respected skaa thief in Luthadel. He had not yet come into his Allomantic powers. He and his wife Mare dreamed of the pre-Ascension Scadrial of gardens, green plants, and no ashfalls. They planned to rob the Lord Ruler, but they were discovered by Inquisitors and Mare was accused of betrayal. Kelsier was sent to the Pits of Hathsin as punishment and forced to mine atium geodes, resulting in severely scarred forearms. When Mare is killed by the guards at the Pits, Kelsier Snaps into his Mistborn powers and escapes. He trains with the Allomancer Gemmel in the north of Scadrial.

Kelsier’s plan to overthrow the Lord Ruler, set up a skaa government, and take hold of the empire’s treasury is dependent on his secret, secondary plan: that of creating a religion among the skaa passionate enough to motivate them into full rebellion.