1. Legend decks are almost always built with mage cards, and mage usually comes with swift, so the player get extra turns and stocks.
2. With cards like meditation and pegasus, to get 30 gems is not too difficult although it's true that gem is the lowest resource at the start of the game.
3. Frost unicorn - For the damage, we compare with another similar card, Imperial griffin. The base attack for imperial griffin is only 19 (35 from unicorn), it needs two other types of card to reach max damage, and it costs 35R. However, from frost unicorn, with 2 other keywords, there is an extra 20 gems in return plus +1 magic. I think its pretty obvious which one is more superior.
4. Moonlight unicorn - the least powerful legend among the 3. The attack here is reasonable I guess, but the swift keyword + a mage card played in the previous turn (which I dont think is too hard to do) would still give 10+ gems in return. If I recall corretly, there is no other cards that has similar benefits. Perhaps, Ceremonial guard but it only does 10 damage.
5. Azure unicorn - the most over powered legend card. With only 12G + 15R and higher magic, it does 34 damage! If the opponent does not have any counter +magic cards, the game would be over. In addition, the legend cards always give a 25% chance that one of the facilities (lowest) will be raised by one. Even if the player fails to draw any +magic cards, azure unicorn is still possible to do the incredible 34 damage.
Any thoughts?