How to get the Telesto emblem in Destiny 2

Turns out that the new Telesto emblem may have been the entire reason the buggy fusion rifle was taking over Destiny 2 the last few days. First, it gained an alternate firing mode where it would spark and shoot out a shower of orbs, then Telesto somehow got the keys to Bungie's Facebook and Twitter accounts, and now we've got a free emblem to claim...
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