Sarin

From Memory Alpha, the free Star Trek reference

Sarin was a Suliban female. While a member of the Suliban Cabal, she received genetic engineering, giving her the ability to shapeshift if she could trust someone, simply by being in close contact with them.

After a time she turned dissident, as she disapproved of the Cabal's aims and methods. Sarin provided Klaang the Klingon with proof of the existence of a Suliban Cabal plan to undermine the Klingon Empire. After informing Captain Jonathan Archer about the Temporal Cold War on Rigel X, she was killed by Silik whilst aiding Archer and his team to escape the planet. (ENT: "Broken Bow")

Later, Colonel Grat learned that Archer and Sarin had met. The colonel asked whether the Suliban female had told Archer of the war, but the captain refused to respond. (ENT: "Detained")

Sarin, in her Suliban form.

Sarin, as she appeared in Human form.