Gravemind

Gravemind is a fictional alien in the "Halo" franchise. It is the hive of the Flood and central form. It is voiced by Dee Bradley Baker.
Fictional biography.
The Gravemind encountered both Master Chief and the Arbiter. It gave them an offer to defeat the Covenant Loyalists.
Development.
For it's first appearance, there was supposed to be a full level about him but was replaced with an opening cutscene.
Reception.
Many people didn't like Gravemind's first design. By the remake for Halo 2, his design was heavily improved and got better reception.