Like other vampires Kain drinks blood to survive, though he has shown a greater level of immortality than other vampires. He implied at one point that the only weapon that could kill him was the Soul Reaver. He posses a variety of powers including the ability to shape shift into a wolf form, an intangible mist, and a group of bats which he uses to traverse long distances or to escape when a fight is not going his way.
Kain has demonstrated great ability with telekinetic manipulation, from blowing down walls, flinging opponents to their death or sucking the blood from wounds while being up to ten feet away from his victim. He is able to leap great distances and control his descent to land silently from the highest ledges.
As an elder vampire Kain has tremendous physical advantages over average humans. Super strength, reflexes, stamina, and durability.
Kain posses great magical ability with demonstrated control of elemental magics like fire and lightning. In addition he has acquired a wealth of nasty spells that range from flaying the flesh off a person's bones to possessing their minds.
Kain's most deadly weapon may be the Soul Reaver, an ancient wickedly curved blade originally designed to draw the blood of it's victims to the vampire wielder. Now the Soul Reaver houses the ravenous devourer of souls, Raziel. As the Soul Reaver dispatches an enemy it tears the soul loose to feed the spirit trapped within the blade. Kain is a skilled swordsman who often forgoes using his tremendous magical abilities for the thrill of dispatching his enemies at the point of the Soul Reaver, often exclaiming. "Vae Victus!." (Suffering, or woe to the conquered.)
"For all our bravado we knew what it meant when Kain drew the Soul Reaver in anger. It meant you were dead."
-Raziel, Legacy of Kain: Soul Reaver
Kain is a calculating manipulator, often using others to reach goals far in the future. He spent years studying the events that unfold in the chloroplast chamber, a window into different times used by the Time Pillar Guardian, Mobias. From his studies he devised a way to go back in time to change the history of his world to bring balance back to Nosgoth.
Seeing the opportunity to put his plans to work Kain had his eldest and most trusted lieutenant, Raziel, thrown into the abyss, where his vampiric body would be destroyed by the swirling waters. Raziel would later be resurrected as a wraith and devourer of souls. The same wraith that would ultimately inhabit the Soul Reaver, which is key to changing Nosgoth's history.