-Gravikor
Great card to beat enemies, that only focus on flying creatures. And even when played, if does not mean the flyers are already dead. The mana cost seems ok to me.
-Circle of Light
Good card against unliving. There are already several Damage Barrier enchantments released, so this should not be unbalanced.
-Plagued
Mana intensive enchantment, that can evaded easily after beeing revealed (after dealt damage once).
-Altar of the Iron Guard
Cheap comjuration with very limited use, when there are conjurations or creatures spread all over the gameboard.
-Summoning Circle
Never seen it used on OCTGN ... probably for a reason. Could work once in a game with a Hydra but you can easily move away from that zone. Seems not overpoweredto me.
-Altar of Peace
Good Card, but harms yourself too ... looks like a different Suppression Orb.
-Raincloud
I was very excited about that card, when it came out. But i stopped using it, because the initial cost is too high. May help in some matchups, but not in all.
-Mordok's Tome
Not very useful for a Wizard, that can prepare two cards and always change his mind and attack with arcane zap anyway. Never seen it beeing used.
-Temple High Guard
This guy is not bad, but if i had the chance i would summon rather a Knight of Westlock (for offense) or a Guardian Angel (for defense)
I do not see overpowered cards here.