Sentinel Prime

Sentinel Prime is the name of several fictional characters in many of the "Transformers" series. First mention of Sentinel Prime was in issue #65 of the US Marvel Comics "Transformers" series, where he was mentioned to hold the Autobot Matrix of Leadership before Optimus Prime. 
Sentinel Prime is One of the members of the Dynasty of Primes and dedicated as the leader of the Autobots and has since appeared in a variety of forms as either Optimus Prime's mentor or friend. In the 2011 live action movie "", Sentinel was the main villain and was voiced by Leonard Nimoy.