Summerstone  

Since this isn't EX can you sell it?

Ru'Aun Gardens is found in what is known as sky. To get access to sky you need to complete ZM1-13 and you need Rank6 in order to activate the Zilart Missions. Although sky is found above Delkfut's tower in Qufim Island, it is accessed by going through Zi'Tah to Ro'Meave to Hall of the Gods and from there a portal will send you to sky ^^.

Trade this and a Gem of the South to a ??? in E-9 of Ru'Aun Gardens to spawn Suzaku, an HNM giant bird.

All the 'seaon' stones have similar uses in spawning HNMs in Ru'Aun Gardens.