So, first off, stealth is close to a lost cause vs Valev. Sneaking around is Valev's bread & butter, and he has plenty of experience on it. His very first job after the destruction of his home realm was as a sniper in a realm of incredibly powerful magical entities, and that was before his time magic and senses were fully developed. At this point and time, Valev's illusions and senses are very likely to turn Iandva's tactics on him; for example, Iandva could go in for an attack, only to be attacking nothing and running into an ambush of the invisible.
AP is just about the same, since both are nearly the same. However, Kiri can screw with durability and greatly increase Valev's damage output.
Speed is where things get bad for Iandva. Valev's amp is quite strong, and Iandva doesn't have a whole lot to compensate for the gap. It seems Iandva has some statistic amplification, but it says he only has 'a little'.
Let's quickly go over Iandva's stuff, now. Darkness Manipulation is strong, but it's not haxy in many ways that would really stifle Valev. Stealth is rather hard countered by Valev's unnatural stealth and Extrasensory Perception, allowing him to see the invisible. Flight is potent here, and could keep him away from Valev's swarms of attacks, but it's not something impossible for Valev to overcome. Non-Physical Interaction in Valev's favor really does hurt Intangibility, too. Energy and Ice Manipulation grant Iandva a bit more versatility. Possession is where Iandva has a bit more of an advantage; Anamnesis isn't really something that can completely no-sell magical, shadow-based possession, although it could help give some power over his body. Granted, this advantage isn't an instant win, since once Valev figures it out he can use light to remove his shadow. I'm not really sure how Iandva's Dura Negation works and how potent it is. Paralysis is countered by Anamnesis.
Overall, Possession seems to be Iandva's best bet, but that's just temporary. What else does Iandva have here, since I'm really not sure that Iandva could take on the Valev Swarm by my analysis. Iandva's weaknesses put him as an aggressive, yet somewhat predictable fighter, which could easily be the end of Iandva if Valev's intelligence kicks in and he sets a trap.