Mordakti

The Kanohi Mordakti was the Mask of Infiltration. It rendered the user invisible to electronic security systems and automated defenses such as robots or mechanical drones. In addition, the user could select one individual being at a time that the user would be rendered invisible to.

Onnyx's Mordakti
Onnyx’s Kanohi as a Matoran would transform into the Mordakti when he transformed into a Toa after being given a Toa stone from Vorils. As a Toa, Onnyx had little use for the Mordakti’s powers until he chose to infiltrate a Black Vulga vessel in search of answers as to the organization’s goals.

Example usage
While onboard a Black Vulga sailing vessel, Onnyx evaded detection from the vessel’s security systems and guards by using his Mordakti. He further succeeded in sneaking onto Vulganau and  infiltrating the Black Vulga compound there.