The Eska were a technologically-advanced humanoid species that were first encountered by the Enterprise NX-01 on a rogue planet called Dakala in 2151. For nine generations, small Eska hunting parties had stalked and killed the indigenous lifeforms on Dakala, seeking in particular the shapeshifting beings known as Wraiths. Captain Jonathan Archer and his crew were able to protect the Wraiths from the Eska by providing them with a chemical masking agent that hid them from the Eska's sensors. (ENT: "Rogue Planet")
Eska are humanoid with a large bony, bumpy, ridge that begins at the nose, goes up the nose and up the forehead, the ridge has two small ridges running parallel on it. They have somewhat thicker brows than Humans that cause slight, smooth ridges from the ridge and over the eyebrows.
When Malcolm Reed and T'Pol were attacked by two Eska hunters, one yelled "Dhk'trrrr! Siskah trrral p'kaaat!", then when the Eska realized Malcolm was a humanoid he told his companion, "Nahk l'taree".