Clash of the Star Trees (CST-000 XR) [Clash of the Star Trees]

[Extension Rule] (This card cannot be in any deck. You can only have up to one card in your extension rule area. You may start the game with this card in your extension rule area. If you do, apply the following text until end of game.) Rulers you own named "Lenneth, Lonely Asteras" and/or "Yggdrasil, the World Tree" gain World Tree in addition to their other races everywhere and have " [Tag] (World Tree)" everywhere. Rulers you own named "Sieben, Malefic $t@r" and/or "Yggdrasil, Malefic Verdant Tree" gain Malefic Tree in addition to their other races everywhere and have " [Tag] (Malefic Tree)" everywhere. Apply the effects of this card already during deck construction and setup.