Question about level up emotes

Hey guys, I hit level 40 recently on the PBE, and I got an emote shard that says Legend 1. I don't know what these are as I've looked everywhere but no one seems to mention them (even RIOT). What are these emote shards, when do you get them, what do they mean ? If there's a RIOT post about it, I probably missed it, and if you could link it, thank you. Here's a pic of the in-game loot:
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