The Challenges are a time-limited event implemented in the game for a pre-determined time that rewards players with all sorts of goodies, exclusive items and rare rewards. They are similar to "Star Week", with which many tankers are already familiar. Challenges give you rewards for the number of 
Stars (a special resource exclusive to such events) earned in battles; and consist of many stages (or "tiers") with each new stage bringing you additional and better rewards. To complete stages, you need Stars - which are earned only in Matchmaking battles.
You can access the "Challenges" window by clicking on the respective tab from the Missions window. In the Challenges tab, you’ll be able to see your current progress in the event, including how many Stars you have earned, how many more you need to complete your current stage, and what the rewards will be when the Challenge ends. Whenever you reach a new stage, you will receive an in-game notification. The rewards for completing a stage are added instantly to your account - unlike most previous Star Week/Crazy Weekend events.
Read more information about the current Challenge on the special site or the official forum topic.
Earning Stars
Stars are earned by finishing Matchmaking battles. When the battle finishes, the players who were in it will receive a number of Stars based on
- their position on the final scoreboard, and;
- whether their team won or lost (this does not apply to solo battle modes such as JGR and DM).
For the exact amount of Stars given, please read below:
- 1st and 2nd places on the winning team, 1st place on the losing team or 1st and 2nd places in solo modes (DM and JGR) — 3 Stars;
- 3rd and 4th places on the winning team, 2nd and 3rd places on the losing team or 3rd and 4th places in solo modes (DM and JGR) — 2 Stars;
- All other places — 1 Star, if you were active during the battle.
You can increase the number of Stars earned by getting a Premium Account. With it, all the Stars you earn will be doubled. This means that you can reach the final tiers with half as much effort.
Increasing your tier rewards — the “Battle Pass”
Challenges have also introduced a new pass into the game — the 
"Battle Pass", which allows you to unlock a set of bigger and better rewards for each stage of the challenge. Some of these rewards can be pretty unique! You’ll be able to buy the Battle Pass at ANY stage of the challenge — at the very beginning, in the middle, or even in the very final stage — and you will still get ALL the rewards from both the top and bottom rows.
The prizes given by the Battle Pass will be stacked on top of the normal rewards (i.e. completing tier 70 will give you both Container XT and Titan Prime skin!). Both levels of prizes will be visible in the interface, so at any time you can see the rewards you’re currently getting, and compare them with the rewards that you could unlock with a Battle Pass. You can purchase the pass directly from the Challenge window - it is sold in the Shop for 500 
(along with 3x Days of Premium Account) and will only be valid for the current challenge (e.g. the pass will disappear after the current challenge is over and you will need to buy it again if you want increased rewards for the next Challenge).
Premium Account players also get additional advantages during Challenges. In addition to its many benefits, a premium account now also double the Stars you earn in battle. This means that if you have a premium account, you will be able to reach the final stage of the challenge (and the biggest, coolest rewards) twice as fast!
Tier Rewards
As you start getting more and more Stars, you will advance up the tiers. The prizes will get bigger and better as you go up. Use the table below for information on the prizes.
Free Rewards
Battle Pass Rewards
Stars Calculator
You can use this simple application to help you manage your Stars during the Challenge.
