Dante

Commander Dante is the oldest living (non-primarch) space marine who is not in a dreadnought. He is the victor of countless campaigns and his deeds are indistinguishable from legend.

In the plot, Sanguinius made a prophecy that there will be some great battle that will kick the asses of all others and that there will be a great, golden warrior standing between the emperor and the darkness. Dante thinks that this golden warrior is him.

He also worked with a Necron army to defeat a Tyranid hive fleet (enjoy your Black Library).