Sangheili Spec Ops
Because one disappearing enemy wasn’t annoying enough.
Sangheili Minors start appearing as leaders around Force Level 6. They upgrade to Sangheili Spec Ops at Force Level 13, and Sangheili Zealots start appearing as leaders around Force Level 18. (They lag a force level or two to appear as followers.)
They use the Halo Plasma Rifle and their own Energy Sword, which upgrade with them.
Their capabilities per tier are:
Starting – Sangheili Minors start with a regenerating shield and Momentum, which lets them reposition after taking a risky melee strike.
Advanced – Sangheili Spec Ops gain Vanish, letting them disappear from enemy sight and freely move and attack without revealing themselves, until it’s too late to react.
Elite – Sangheili Zealot gain Retaliation, enabling them to take a reaction shot to any hostile action within their line of sight.
In lieu of an autopsy bonus, they instead have the chance to drop refraction field items or alien alloys, depending on your luck.
Thanks to Bungie, 343 Industries, and MIcrosoft for the Halo series, where the original assets came from.
Thanks to Condensed Turtle Flesh for porting said assets to XCOM.
Thanks to HotChocletyLez for porting and making the animations for proper Covenant weapons.