The initial release of Artifact will contain 280 cards and 44 heroes
There are a couple of confirmed card types, namely Heroes, Spells, and Items.
Spells cost mana, which is spent from a pool of mana in each lane. Spells require that the player has a hero in the lane of the same color as the spell in order to cast it.
There are four card colors: Red, Blue, Green, and Black.
Item cards are purchased during the shopping phase from the Secret Shop. Item cards cost gold, which is acquired by killing Creeps and Heroes. Players receive 1 gold for killing a creep, and 5 gold for killing a hero.
Here you can see the list of cards.