This player's champions are immune to psionic attacks. Champions with attached artifacts or magical items cannot attack this realm, although they can be added during battle.
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TSR
Wizards of the Coast
All of a player's champions are immune to offensive psionic powers when this Dark Sun realm is unrazed. Among these are psionic power cards and offensive psionic abilities of champions and allies. All monsters in the player's pool are protected from Agis (261/3rd) special power as long as Ur Draxa remains unrazed. If your deck is heavily dominated by monsters, this can be very useful. A psionicist-based deck can also be almost completely disabled by this realm.
Ur Draxa also limits the potential attackers in addition to his immunity. This realm cannot be attacked by any champion with an attached magic item or artifact. In order to attach items to Ur Draxa, a champion must first begin the attack. In addition to champions brought into battle with cards like the Helm of Teleportation (219/1st), this restriction on attachments extends to them as well.
This realm, as well as a few other Dark Sun realms, doesn't have it's own realm champion. However, you attach Silver Spring (97/4th) to it, and it will become more dangerous.