Onyx Sentinel

The Onyx Sentinel is a Forerunner-created electromechanical variable configuration and purpose machine. It has only been seen on the Forerunner artificial world known as Onyx, which was actually comprised of trillions of the machines. Whether the same model is on other worlds is currently unknown. It is a variant on the Standard Sentinel design.

Appearance
The Onyx Sentinel could possibly share a similar appearance to the Monitors - with a round sphere in the center, and with a central "eye" that glows golden. The eye is the weaponry and offensive capability of the sentinel as it charges and unleashes what appears to be a devastating array of energy. However, it also has three metal booms extending from equidistant points on the surface of the central sphere.

The Onyx Sentinel also has anti-gravity technology, similar to that of the Covenant. Although the Onyx Sentinel can even reach escape velocity and fly into outer space, in ground operations, it normally engages its targets at a height of three meters, working a "Higher Ground" battle mentality. It is also able to attenuate its booms to the signal of UNSC COM channels, and can actually speak the Human archaic language of Latin.

Combat
The Onyx Sentinel is infamous to be the most dangerous classification of known Sentinels, is extremely versatile, and is a powerful combatant on both the ground and in space. One of their primary advantages, is a gold-colored Energy Shield that is entirely resistant to all projectiles, even the rockets of the SPNKr Launcher and LOTUS Mine detonations; however, the shield is duped by slow moving objects, such as a rock, which was used to destroy one Sentinel on Onyx. It is unknown why the shields only snap into place when fast moving projectiles are coming in the direction of the Sentinel. (It is unlikely that they due so to conserve energy, for the enormous output of energy per beam is far greater than the amount used to hold shields in place.)

It is also very adaptive, each Sentinel transmitting its combat footage to an unknown intelligence that continually upgrades Onyx Sentinel combat algorithms. As per a Spartan: "We are teaching it how to fight." The Onyx Sentinels can also merge together for a variety of purposes, such as combining to increase firepower and shield strength, architectural purposes, and forming clusters to protect Onyx.

It is far superior to the regular Sentinels that guard the Halo ring-installations and The Ark and even the Sentinel Majors of Installation 05 due to its shielding and extreme firepower. Onyx Sentinels fire golden, lethal spears of light from a central eye, which is thought to be similar in strength to the beam weapon fired by 343 Guilty Spark at the end of Halo 3. This attack causes devastating damage: the destruction of a granite plateau, vaporization of a combat bunker, and the instantaneous destruction of any ground vehicle or infantry,even including a SPARTAN-III. Enough Onyx Sentinels (about 45) can even vaporize a large starship with apparent ease.

Concept Art
These are some fan made concepts of what the Onyx Sentinel may look like. Note: This is Fan Art and is not a confirmed image of what the Sentinel looks like.