Sharquoi
From Halopedia, the Halo wiki
In the Conversations from the Universe booklet found in Halo 2: Limited Collecter's Edition, an Elite refers to something called the Sharquoi. This has been assumed to be another Covenant race. In a deleted scene, a mural can be seen showcasing the Covenant races, including a very large creature assumed to be a Sharquoi. Because of its similarity with the Drinol, many speculate they are the same, but Bungie has not confirmed or denied this. Another theory states that 'Sharquoi' is the name of the Forerunner Ship in whice the Prophet of Truth embarks from High Charity at the end of Halo 2.
From a Bungie Weekly What's Update:
Q: What's a Sharquoi?
A: Very freaking dangerous.
Frankie has talked about playing Halo 3, and fighting Grunts and "something larger than a Grunt," supporting the idea that the Sharquoi will be seen in Halo 3. [1] KP also mentions fighting Grunts and a "CENSORED". [2]
