There's a Banner Lords targeted champion boost going on in the game right now - nice, but it offers virtually nothing for players who don't have a stack of sacred and void shards, or perhaps a huge pile of ancients (and the ancients won't help much for the summoning event, but that's another discussion...).  

Why not include 1 void rare and 1 or 2 non-void rares in such faction-based targeted boosts, next time? Then f2p players or paying ones who just don't have a lot of shards available, might also try to use their limited ancient/void shards for specific rares they don't have yet, whether it's to use in teams or for a fusion. Or just because they want to check all the boxes in their index. 

Or even make it a general thing for all categories of champions, including commons and uncommons on the mystery shards. Most players won't care about those, sure, but it makes it accessible to all players however low their level, and some early-mid game players might still want a certain uncommon or just more options for their first faction wars team.