The SST Laboratories B73 Siege Automaton "Bastion" were the basic infantry type of SST Laboratories Siege Automaton.
This type of Siege Automaton appears as Bastion's "Omnic Crisis" skin.
B73s were heavily utilized by the Omnic rebel army during the Omnic Crisis, acting as infantry for the army. They were involved in the attack on Eichenwalde. After the crisis, every B73 was destroyed.
Upon awakening, Bastion discovered the body of a B73 and utilized it's memory chip to gain knowledge of the battle that had occurred years ago.
- Main article: B73-NS
In preparation for the King's Row Uprising, Null Sector re-engineered and upgraded some SST Laboratories B73 Siege Automatons into B73-NS models, who were greatly superior to the original B73s and could take on the Configuration: Tank.