Well, I don't think a Time deck would really be interested in a 1/3 better Supernova. For more than twice as much. If they would use each of these colors, then why wouldn't they use a Supernova instead?
And the Stone Guardian idea is somewhat OP. Allow me to explain by way of breakdown.
Earlier, there was a Time creature suggested with the same power. I would look up who posted it, (I think it was called Clockmaker, or something) but ultimately it is unimportant.
That creature was:
1) Decidedly uber-rare.
2) Had a toughness of 3, not 8. Ergo, fairly killable.
3) He also placed himself in a bubble, making both creatures sit out for a turn.
4) Was mono-Time (keeping the ability in the family, as it were), and not part of a two-color combination that is commonly understood to be more powerful than that.
And even then, was relatively OP.
If all else was identical about this creature, but it was part of a two-color combination not commonly employed, like water/time or something, than it would give that combination power, and decks would be built around it. As it stands, enough people recognize that Earth/Time has enough (possibly too much) power when compared to other elemental combinations.
Sorry, I am not trying to only shoot down your ideas, I just don't have time right now to offer suggestions on fixing it. But good job on card design and art, I think I can see the direction you are trying to go with these cards, and I look forward to seeing the evolution of the time-bubble creature idea.
