Galactic archaeology is the use of the velocities and abundances of stars to learn about the history of galaxy formation and nucleosynthesis. I will tell three stories of galactic archaeology with three different groups of elements: alpha elements, the iron peak, and the r-process. All of these measurements were made with the Keck/DEIMOS multi-object spectrograph.
First, I will present detailed abundances of individual stars in the dwarf satellites, stellar streams, and smooth halo of M31. The evolution of [alpha/Fe] in these stars supports the hierarchical assembly paradigm of galaxy formation.
Second, I will present abundances of manganese and nickel in dwarf satellite galaxies of the Milky Way. These abundances are best explained by a strong contribution of sub-Chandrasekhar-mass Type Ia supernovae.
Third, I will present measurements of barium abundances in the globular cluster M15. The constancy of barium from the main sequence to the red giant branch indicates that the stars in M15 were born with their unusually large dispersion of r-process elements rather than acquiring it from an external source.