How to get to the hidden location for shopping in the Oasis in Krokotopia:
Go to the lower island (next to the entrance to the Tomb of Storms) where the other stores are, and you will see two obelisks with a portal in between them. The obelisks have an hourglass on the bottom of them.
The red vertical lines on the obelisks with circles represents an approximate 10 minute period. Every 10 minutes, another circle fills red. After the entire obelisk is filled red, the obelisk top will shine, and the portal in between the obelisks will be active.
Step on the portal, and you will have access to a hidden market run by Sed Talam. On top of the small building in the market, there is also a card trainer named Tish'mah (for Myth School).
P.S. - You can go to different realms and each realm is on a different timer, so some realms may have more or less circles filled on the obelisks.
Every 10 minutes it lights up so you can go in and it is a cool place and they even have a pet there! So you should check it out! If you dont want to wait 10 minutes then try switching realms. Hope this helps!