Colossal can be trained at level 64, but the side quest Bungle in the Jungle and the following quest after that must be completed. The Bungle in the Jungle side quest can only be gotten once you finish the quest For My Next Trick which is a storyline quest in Zafaria.
Epic can be trained at level 110 from the Arcanum's Astral Scholar.
Strong, Giant, Monstrous, and Gargantuan treasure cards can be found in the Astral section of the Bazaar.
At your level you can only use the TCs, at higher levels you can train these "damage" enchants in Celestia, the TC you want to look for is Monstrous, I believe the first world they sell them is celestia, but you can find them at the bazaar sometimes or ask a higher level wizard to buy some for you and trade
I believe that certain spell is a sun spell. You can use training points to learn it in Celestia, starting with Strong. The card you're talking about might be Tough, though, and it might only be a treasure card.