Generally, the foils from Masters sets tend to be worth less than foils from other sets, but Masters 25 seems to be an exception
Key characters include Ariel, the adventurous mermaid
Aethertorch RenegadeAethertorch Renegade can make that happen if you've got a lot of energy laying around, which you very well might if you've found a way to take advantage of its four energy for three mana efficiency on more than one occassion
So if you can threaten those creatures without spending cards (graveyard cards don't really count the same way), you are slowly gaining an advantage with each activation
Bristling Hydra: [Category 2] ETB yield is 3 Energy for 4 mana, then you can spend 3 Energy to place a +1/+1 on this creature and give it end of turn Hexproof
Its market value is around $131, but its selling for more if you do happen to have one