If you are no longer able to use one of your champions, it is most likely due to one of the following reasons:
1. The champion's free rotation has ended. Free rotation lasts for a week, and once that week is over, a new set of champions will replace the old set in the free rotation roster. If a champion is no longer on free rotation, you must buy that champion if you want to keep using her.
You can check the current free rotation by tapping the gift box icon at the upper right corner of the main menu.
Then tap "Free Rotation" in the menu on the left side of the screen.
2. The champion's trial period has ended. Sometimes you can win trial versions of champions as event prizes. Trial versions of champions (as well as weapons and skins) will always have a time limit listed after their name, so make sure to check the details of the rewards when you participate in an event.
Once the trial period is up, you must buy the champion if you want to keep using him.
3. The champion has been temporarily disabled. On rare occasions, we must disable a champion due to a bug or a redesign. We will always post an announcement before we do this, so make sure you check the forum for the latest news. You will not be able to buy a disabled champion. If you have already bought that champion, you will not be able to use her.
You will not receive any compensation if one of your champions has been disabled, because you have not lost the champion. Don't worry; the champion will be restored to your account when we have re-enabled him, and all of his Talents and weapons will remain intact. You will not need to buy the champion again.
If for some reason you do not receive your champion back when she has been re-enabled, or if you have lost a champion under circumstances not covered in this list, contact customer service.