These are analogues of the battle pass system that is used in many games.

Mighty Pass

Mighty Pass can be found in the bottom left corner of the main screen.

Each Mighty Pass lasts exactly 21 days and is reset after this time.

When you complete Daily and Weekly quests, you receive Mighty Points which help you progress through the Mighty Pass steps.

If you don't have enough Points, you can purchase levels with Gems in the Mighty Pass window. Purchasing Levels becomes available when you have 7 days or less until the Mighty Pass reset.

You can receive rewards from the bottom bar for free, but to unlock rewards from the upper bar, you need to purchase Premium.

Premium gives you additional rewards from the upper bar.

There is also an option to purchase Premium+ which not only gives you access to additional rewards, but also affects your Mighty Pass progress, granting you 8 Levels right after the purchase.

Event Pass

Event Passes are active during Events (Global ones and Chosen Hero).

Unlike Mighty Pass, Event Pass has 15 Levels. To progress through them, you need to complete Event Quests and collect Event Points.

Levels in Event Pass cannot be purchased with Gems or any other resource.

As well as in the Mighty Pass, rewards from the bottom bar are received for free, but to unlock rewards from the upper bar, you need to purchase Premium.