The Heavenly Hosts or the Host were angelic service robots working for Max Capricorn Starcruisers. Under the command of Max Capricorn himself they killed the passengers and crew of the Starship Titantic in 2008 as part of Capricorn's scheme to destroy his own ship and then retire a wealthy man. After Capicorn's death, the Host obeyed the next authority figure - the Doctor - and aided him in his saving of the Titanic.
The Hosts speech pattern involves starting a sentence with "information" and then the answer to a query. Protocol 1 allowed the person who executes it to ask three questions, which would temporarily overrides whatever command they have until the three questions have been asked.
The Hosts used the Halos on their heads as weapons to them at enemies. They could also fly. Some of the Hosts were destroyed by an electromagnetic pulse set off by Bannakaffalatta, who used his cyborg body to destroy a number of them, at the cost of his own life. (DW: Voyage of the Damned)