First I'm going to say an unpopular thing, I like fragment events more than Fusion events, it's more straight forward, I don't need to level up and ascend heroes that I would sacrifice.

That said, I think there's things you can improve on how fragments wotk.

THE PROBLEM OF LEFT OVERS FRAGMENTS

Either by getting more than needed or simply unable to collect all 100 fragments, players are left with unusable fragments. So what are we going to do with them?

I suggest that you make a fragment store, where players use a number of generic fragments to "directly buy" a specific champion of Plarium's choosing. Ranging from Rare to Lagendaties.

These "generic" Fragments are not the same as the specific champion fragments that we get from these fragment events. My suggestion is that after a fragment event is finished you present an option for players to exchange their specific Fragments they collect from the events that they can't use (leftovers) into these generic fragments.

This way, early players who can only collect say 70 fragments can turn their fragments into an Epic champion from the list provided by Plarium in the fragment store, and not walk away empty handed.

This also means veteran and big spender players have reason to get the extra fragments, and not just the 100. Which would mean more players spending on refills.

The list in this store can be static, or Plarium can rotate the list to their liking, maybe even make certain champions only available in this store. Heck I'd suggest the Drexthar fragment you sell on Bazaar to be turned into these general fragment, and put Drexthar as one of the list champion in this fragments store.

This way, players don't wonder around when will the next event of specific champion fragment event will comeback, and Plarium can have more freedom in making future fragment events. This way you can also sell the fragments to an even bigger audience, not just to those who were unable to finish the fragments events.

Well that's my feedback.