If a card has been FULLY leveled then instead of 5% of the stats it retains 10% of the total stats

 If a card has been FULLY leveled then instead of 5% of the stats it retains 10% of the total stats. 

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 If a card has been fully mastered, in addition to having a higher attack and defense rating in the new form it ALSO will retain HALF of the total mastery for the new card making it quicker to master in its new form.

 

Ultimately what this all means is that you should never fuse a card you plan on using in your deck until it has been BOTH fully LEVELED and MASTERED or the card you end up with will NOT have its full potential actualized.  This process can take a long time, but it trashes the trade value of your cards if you create an 

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“imperfect form” by not fully leveling and mastering it before fusing.