The Graak was an amorphous being created by the Fourth Doctor.
Biography
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 Determinent. He gave it full movement capabilities and kept in touch via a telepathic link. (VG: Destiny of the Doctors)
- Exactly which of the Doctor's regenerations created the Graak is unknown; it is assumed to be his fourth incarnation, based on the fact that the Graak first appeared in that Doctor's TARDIS.
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. (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, but during the final battle against the Master, it willingly sacrificed its remaining life energy to save the Doctor, showing a capacity for heroism.
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
The Graak is only able to be seen using the cameras view in the Doctor's TARDIS. It is sometimes referred to as a "jelly-fish like blob" by some fans.