Captain.

A leader of an entire company. When a company's previous captain has died, the lieutenant of that company with the greater leadership skills will take his place. If neither of the lieutenants are dubbed worthy by the Chapter Master, then a battle brother from the first company will be chosen. A captain has authority over all marines in the company.

They commonly where capes and adornments on their helmets. They wear the standard colours for their chapter.

A big difference between captain and the lower ranks is that they are involved in negotiations with both other chapters of space marines as well as other factions in the Imperium. They must be more then skilled warriors or tactions. They must be diplomats. Cunning and shrewd. They must also be inspiring as they will be used in the empires propaganda reals.

Once a captain, a space marine will be allowed multiple alien slaves rather then just 1. However the number of slaves is not allowed to be larger then the number of human's in their harems.

They are given different titals depending on what company they lead.

1st: Master of the Watch

2nd: Master of the Arsenal

3rd: Master of the Fleet

4th: Master of the Marches

5th: Master of the Rites

6th: Cheif Victualler

7th: Lord Executioner

8th: Master of Relics

9th: Master of Recruits

The rank of captain is allso bestowed to the leaders of specialist groups in a chapter.

Captain of the Chaplains: the Master of Sanctity

Captain of the apothecarys: Apothecarion

Captain of the Tech Marines: Master of the Forge

Captain of the Librarians: Chief Librarian

Some chapter's call captains different things. The Dark Angels call them Masters. The Raven Guard call them Shadow captains. The Space Wolves call them Wolf Lords. etc