Here's a handy reference for you:
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- Life Points: 99
- Max Mana: 99
- Units in play: 6, plus your Hero
- Hand: 9 Cards. Any additional card draw will send the oldest card in your hand (aka your leftmost card) back to your deck.
- Attachments: all Heroes and Units can have only 1 attached spell or enchant on them at any time. Any new attached spell or enchant they gain will overwrite any old one.