The Graak

The Graak was an amorphous being created by the Fourth Doctor.

Creation
The Graak was created by the Doctor as a means to try and find an escape from the Master after he had trapped the first seven incarnations of the Doctor in the Determinant. He gave it full movement capabilities and the ability to keep in touch with all of the Doctors via a telepathic link. (VG: Destiny of the Doctors)


 * Exactly which Doctor created the Graak is uncertain. It's generally assumed to be the Fourth Doctor based on the fact that the Graak first appeared in that Doctor's TARDIS and a line of the Fourth Doctor's dialogue in which he identifies himself as the Graak's creator, though the possibility that he was referring to one of his other selves in the first person exists.

Freeing the Doctor
The Graak was on its mission to free the Doctor almost as soon as it was created. Starting in the Fourth Doctor's TARDIS, it set about retrieving various objects to get across the Great Divide, after which it would free the Doctor who was in this "time zone".

Throughout its quest, it was slandered endlessly by the Master, who tried to use various means to stop the Graak from accomplishing its task. He even attempted to hypnotise it on at least two occasions.

After several quests and mental challenges the Graak freed the Doctor, at the cost of its own life. (VG: Destiny of the Doctors)

The Heart of the TARDIS
The Master had actually sent the seven Doctor's into the time vortex, and they had ended up in the Heart of the TARDIS. The Graak's energy levels were waning, and the TARDIS was on the brink of destruction.

Making its way through water-filled caves and into the Heart, the Graak used up its remaining life force to materialise the Doctor's into the TARDIS, saving the Doctor's and the TARDIS, but killing itself in the process. (VG: Destiny of the Doctors)

Personality and abilities
As a telepathic entity, the Graak had no clear personality or emotions of its own, but during the final battle against the Master it willingly sacrificed its remaining life energy to save the Doctor, showing a capacity for heroism.

Although it floated just above the floor without any visible legs, the Graak was capable of basic movement such as running, jumping and crouching. It was also able to swim, though it did this with a slight degree of clumsiness.

The Graak could also transfer itself to cameras in certain rooms of the TARDIS to get a different vantage point.

It was able to channel massive amounts of energy on a single spot, but this rapidly drained its life force. (VG: Destiny of the Doctors)

Behind the scenes
Doctor Who: Destiny of the Doctors is primarily played from the Graak's first-person point of view. The Graak itself is only able to be seen using the security cameras in certain parts of the Doctor's TARDIS.

The Graak speaks in a deep distorted voice during certain points in the game, but its voice actor is uncredited.