If you want to own Super Belt and Legendary Artifact, you must kill this BOSS to own special items to make it.
Spicifically:
In order to summon 5 BOSS in Emperor's Arena. You must have Dragons Summon Card.
When you have enough 10 Dragons Summon Card, go Emperor's Arena to find Sun Yue[92,137] to summon BOSS
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There are 5 BOSS for each summon. BOSS position in turn appears
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BOSS drops Dragon Jewelry, Spirit Stone, Blood Stone, Child's Food, Cotton, Silver Lvl 2, etc...

Beside, Leaping Dragon will be adjusted about DROP rate.
Now, Leaping Dragon at Twin Island will drop Artifact materials like Nu Wa Stone, Nu Wa God Stone, Blood Stone, Dragons Summon Card, Synthesis Spell Lvl 2, etc...
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For more details about Dragons Summon Card, Super Belt. See at here:
Link

<3 Best wishes for u