Chrysalis is the queen of the Changelings and a secondary antagonist of the season.  She's brought into play around episode six or seven, where Megatron offers an alliance--in exchange for technology to improve the hive's arsenal, Chrysalis will give Megatron foot soldiers to handle the ponies for him.  She's as manipulative and cunning as can be, but is uncertain for how long this alliance will last before one stabs the other in the back.