The Tri-Sentinel is a Sentinel created by Loki, that is a villain from the Marvel Comics and an enemy of Spider-Man.
The Tri-Sentinel is a 60' ft robot sentinel, weighing over 220,000 lbs. It has three pairs of arms, and has three faces on it's head.
Creation of the Tri-Sentinel
The Tri-Sentinel was apparently created by Loki. Loki created it by merging three different types of Sentinels. It was sent to kill Spider-Man when he was Captain Universe. Captain Universe was able to defeat the Tri-Sentinel.
Some time later, the Tri-Sentinel later reappear again to fight Spider-Man but without his cosmic powers. With the help of Captain Nova they were eventually able melted the sentinel's head, defeating it, hopefully, forever this time.