Currently, Light is the only element with a 15/12 cost spell. I propose these to change that (some elements missing)
Fire
Water
Monster from the deep
Summons blue crawlers equal to the number of water pillars/towers you have. Upped summons Abyss crawlers.
Gravity EVIL HAMSTER, MR. JELLYFISH, KUMELEKAR
Black Hole
X starts at 1
Deals X damage/turn to inactive player. X increases by 1 every turn.
OR
Destroys every creature on the field, frind or foe.
Aether
Spatial Rend
Deals damage equal to 20% of opponent's health, so as not to be an end game instant-win card. You would want to get this out early, so it can do most damage.
Entropy
Unkown Entity
Deals damage from 20 - 40, upgrade can damage opponent or heal user for 20 - 40.
Time
Time Bomb
Opponent has 5 rounds in which to win, otherwise they lose. Can only be used if user HP is lower than 50%
Life
Rejuvenate TERROKING
Remove all status effects from you and your creatures
Death
NAME UNKNOWN TERROKING
Generate <a number> of bone/graveyards
OR
generate <a number> of (elite) skeletons
Darkness
Gate of Hell (non-destructible permanent) SCAREDGIRL'S IDEA
summon a powerful Demon to fight on your side. Only problem is that once those Gates of Hell have been opened, you have to win the game in 5 turns. Because if those Gates are open for too long, Demons will come and kill YOU.
Earth KUMELEKAR
Cataclymic Tremors
Destroys all permanents on the field, frind or foe.
Air
Biting Wind
Deal damage equal to 5X the number of air creatures that you have in play.