Like most Magic: The Gathering cards, the value of Kasla, the Broken Halo depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (March of the Machine Commander)
These spells can be used to throw off opponents, create incredibly powerful fusion monsters, and search for key cards with ease
But more importantly, how well do the cards capture the flavor of the Final Fantasy Universe
The more ways you can play by adding mana on the battlefield, the more likely you are to play the large game-changing effects that Ulalek and the other Eldrazis can do to guarantee a win
If a face-up "Infernity" monster(s) you control is destroyed by battle, or leaves the field by an opponent's card effect, while this card is in your GY: You can Set this card to your field