Like most Magic: The Gathering cards, the value of Summon: Shiva 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 (Final Fantasy)
This also gives the giant on this card an otherworldly air
The setting is pretty magical, and you get the feeling that youre accidentally walking upon this rare shining Pokemon in the wild
Bring them back next turn with Call of the Atlanteans to Tribute for Abyssmegalos double-attack effect and destroy even more cards with your Atlanteans tactical abilities
Id like to see this planeswalkers second ability be a -2 instead of 3, or have the first ability be a +2 instead of 1
In addition to the kingpin, both Renegade Map and Prophetic Prism help you keep less than perfect hands as they'll easily fix any of your mana problems