You can check the explanation on the shop:
"There are a total of 14 special Airdrop characters that will be unlocked throughout the Untamed sales event.

Only until a character is unlocked can it be obtained via card packs. For every 100,000 Untamed packs sold, another character is unlocked. When a character is unlocked, all players who have previously purchased a pack receive a random distribution of the new character. Buying more packs will increase your chance of obtaining cards from the Airdrop. There is no guarantee that buying packs will result in receiving bonus cards, however buying more as early as possible will increase the number of opportunities to be rewarded."

The airdrops give you some chance to get the summoner but there is no grantee.