The Saber Cat is the Assembly faction pet. Only members of Assembly may tame this pet, which is found in Nexus Tower. Doctor Overbuild sends the minifigures off to Coalessa, who gives them a misson to find the Saber Cat pieces from the Skeletons on Crux Prime and then return to Doctor Overbuild, and he will build the Saber Cat with the pieces you got for them. Once built by Doctor Overbuild , the Saber Cat runs away. He sends them to find and tame the pet, found by using the Assembly Panel/Console next to Torbert Oscillator, in the Assembly Storeroom. There is no cost for taming this pet.