Kiv

Kiv was the leader of the Mentors and the direct superior of Sil during the late 24th century.

Biography
Kiv helped the Mentors become rich from profitable deals, and was worshiped by many members of his race, particularly Sil. He was involved in weapons dealing with the primitive peoples of the planet Krontep in 2379.

Kiv's great intelligence and business expertise were likely due to his mutated brain, which was vastly larger than the brains of most other Mentors. However, Kiv's brain did not stop growing larger as he got older, and later in his life his brain was compressed against his skull, which caused him severe pain and would have eventually resulted in his death. To prevent this, he hired the scientist Crozier to find a way of transferring his brain into a host who could hold his expanding brain without trouble.

The first operation performed by Crozier moved his brain into the body of a similar Mentor, albeit tan-coloured and with a stinging barb. Kiv's second body held the brain for a bit longer, but was not a perfect solution - not least due to the fact that the mind of its original owner, a fisherman, kept influencing Kiv's business decisions.

When the brain started getting too large for the second body, Crozier tried a different technique and transferred Kiv's consciousness directly into the body of Peri Brown, destroying her original mind and removing the problem of Kiv's constantly expanding brain. Shortly afterwards however, King Yrcanos, who had fallen in love with Peri, broke into Crozier's laboratory. Discovering what had happened to her, Yrcanos killed everyone there, including Kiv. (TV: Mindwarp)

Accuracy
Due to the Matrix being altered, elements of Kiv's biography may be incorrect. Since it was subsequently revealed that Peri did survive the events and subsequently married Yrcanos, it is probable that Kiv actually died before Crozier's final experiment and his consciousness never made it into Peri's body. Alternatively, Kiv may have survived Yrcanos's attack and been transferred into the body of someone other than Peri. (TV: The Trial of a Time Lord)