The boosters are improvements that you can add to your Rumblers during a limited amount of time to boost their abilities.
To be able to add them, your Rumblers must be at the minimum required level.
Boosters can be found by opening every type of chest, from the smallest to the largest. This last ones have a higher probability of bringing them, even the legendary boosters.
They are not available to direct purchase on the daily items store, so you have to find them only on the reward chests.
You can add a booster to your Rumbler at any moment, even if it already has another one connected to it and not yet expired. The game will only ask for a confirmation to override the old booster but, watch out! You are going to lose the old one and you can’t recover the remaining days.
When use time finishes, the booster will expire. You can renew it by using gold. Following you'll see a table that includes the cost for each type of booster depending on the amount of times you have already renewed it:
| Renewals | Core | Pro | Superstar | Legend |
|---|---|---|---|---|
| Once |  1000 |
2000 |
3000 |
4000 |
| Twice | 2000 |
4000 |
6000 |
8000 |
| 3 times | 4000 |
8000 |
12000 |
16000 |
| 4 times | 8000 |
16000 |
24000 |
32000 |
