Agile Chassis is a passive feature that grants a creature 
Advantage on 
Dexterity saving throw and an additional 9 m / 30 ft movement speed.
Description
The lightweight build of this Steel Watcher grants it Advantage on Dexterity Saving Throws and an additional 9 m / 30 ft movement speed.
How to learn
Used by creatures: Steel Watcher (creature), and Hellfire Watcher