Hero Card Packs grant you a fixed number of hero cards of the shown rarity.
 Blue cards represent Common heroes, and Purple cards represent Rare heroes.

When you open a pack, all cards are randomly distributed among the heroes you have reached the unlock level for within that rarity. Each unlocked hero of the same rarity has an equal chance to be selected, there is no weighting or preference, and opening multiple packs does not change these chances.

A single pack may grant multiple cards for the same hero, as long as the total number of cards matches the amount shown on the pack.

While the specific heroes you receive are random, the rarity and the total number of cards are always fixed and guaranteed.