There's a strange artifact included in your victory-spoils. Zavala will want to see this. Report to the new H.E.L.M. space with your findings.
The H.E.L.M. can be accessed via the Tower director map.
You've dealt a serious blow, but Empress Caiatl is not the type to give up so easily. Though she has yet to officially declare war, she has issued a call to all Cabal commanders to prove themselves worthy of a seat on her War Council. It seems the tank on Nessus was one Commander Dracus's answer to that invitation.
This escalation of tensions cannot be ignored. Zavala has designated a new space in the Tower—the Hub for Emergency Logistics and Maneuvers—for handling this crisis. Report there for further instructions.