What level and school are you, and what treasure card are you asking about? Tell us the name of the spell, and also where you're trying to use it. Some cards are level restricted, some can't be used in PVP.
In general, you should be able to cast any treasure card that you have enough pips for. As an example, if you have a Minotaur treasure card that requires 5 pips, then you'd be able to cast it with 2 or 3 power pips if you're Myth or have a Myth mastery amulet; but you might need to wait five whole turns (for 5 pips) if you are a different school and don't have Myth mastery.
hi, how does the treasure cards work, and at what level, as mine is grayed out at level 35
Treasure cards work by certain levels. Some higher rank treasure cards require a higher level. For example, the treasure card for Gargantuan is only allowed for level 55+ players. The "Polymorph Pteranodon" treasure card is for level 75+ players (I think). Try going to the Wizard City Bazaar and search for usable treasure cards for your wizard. They really do make a huge difference in combat!
Sincerely, Victoria ThunderCloud, Level 68 Necromancer
Don't remember when they become active but they are a one time use. If you look at your deck you can click on the gold/yellow treasure card icon which will switch you to the treasure card section. Then you can load up whatever treasure cards you have and when in battle you can discard a card and replace it with a treasure card. Again the treasure cards are a one time use. You can also find info on them I believe in your spell book just click the help icon.