We have created this spot in our FAQs to help players find out which Planeswalkers are currently available in the Shop and when they'll be replaced.
The Planeswalkers available usually rotate on Sundays at 8:00 AM UTC. Special events may change this - please check below. 
 

Planeswalkers currently available in the Shop

The following Planeswalkers are available from March 22nd to March 28th:

      • Karn, Scion of Urza                                                    
      • Mu Yanling, Sky Dancer                        
      • Sarkhan, Fireblood                        
      • Teferi, Temporal Pilgrim                        
      • Vivien, on the Hunt                        
      • Wrenn and Realmbreaker                        
      • Arlinn, the Pack's Hope                         
      • Venser, the Sojourner                        
      • Jiang Yanggu                        
      • Elspeth Resplendent

The following Planeswalkers are available from March 29th to April 4th:

      • Karn, Scion of Urza                                                    
      • Grand Master of Flowers                        
      • Comet, Stellar Pup                        
      • Lolth, Spider Queen                        
      • Chandra, Hope's Beacon                        
      • Gideon, Ally of Zendikar                        
      • Kalemne, Disciple of Iroas                        
      • Teferi, Hero of Dominaria                        
      • Tezzeret, Master of the Bridge                        
      • Ral Zarek                        

Please visit back here often to get the latest information on the current available Planeswalkers. Given the increasing number of Planeswalkers and Card Sets in-game, we are starting to rotate Planeswalkers and Card Sets in and out of the Shop to put a larger focus on the newer sets and keep the game feeling fresh. But don’t worry; you’ll still be able to use any cards or Planeswalkers you currently have in your collection. You’ll also see all the older Planeswalkers and Card Sets returning to the Shop in the future, and you’ll be able to earn cards from older sets in-game. 

Thanks for playing Magic: Puzzle Quest!

P.S.: If you don't see one or more Planeswalkers available in this list in your Shop, it means you already own that Planeswalker. The game won't offer you the Planeswalker you already have, as there is no point in purchasing a second copy of it.