Which rare champion is it?

It's Templar. I raised him up to 6* and he's been good, especially with Ashel, but was needed for the fuse with Relickeeper.  I got a very strong recommendation for Relickeeper from one of the youtube gurus - jgib I think - so I decided to let Templar go. However, there was an option to just give up all his artifacts for a pile of silver, and so I still have him with his 6* if I need him for Factor wars or whatever.  Thanks for responding - it worked out ok and I learned something about the process.

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Relickeeper is epic. Templar is not bad but actually nothing special. If you would like a copy of him, just farm campaign 8 ("Valdemar Strait") - this is where Templar drops.

100% do not use the 6 star templar in the fusion.  You've spent the resources and energy getting him to 6 and he will be much more useful than starting over with another champ.  Even in the long term he will help you with Faction Wars as well as the Magma dragon in doom tower.

As max said above, just farm the campaign stage for a second copy.  

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  Thanks for  the  reply. Fortunately I still have Templar  with 6 stars  but I will have to replace his gear.  So  far not too  impressed with Relickeeper but I will take him to 60 and see. Thanks!

dont rank up relickeeper, he is terrible