Typically, Heirlooms in Apex Legends are incredibly difficult to obtain, only dropping through Apex Packs. Respawn has announced they're overhauling the way that Heirlooms are earned for different characters.
"We're changing up the Heirloom system to make it easier for you to acquire the Heirloom you want," a blog post on the Apex Legends website reads. "You'll now receive Apex Shards. You can then use those Shards to pick the exact Heirloom set you'd like. The Shards will have the same drop rate as the previous system, so after 500 Apex Packs, you will have enough Heirloom Shards to obtain an Heirloom set from the Heirloom shop."
So whereas you'd previously earn an entire Apex set through an Apex Pack, you'll now earn the currency to purchase the Heirloom set of your choosing. Heirloom sets include a unique melee weapon, like Wraith's knife, a banner pose, and a voice line to round out the set. Not every character in Apex Legends has an Heirloom set, and you can see Octane's new special knife just above.
They're incredibly rare. It's unconfirmed if you'll have enough Heirloom Shards after one pull in a pack to buy an entire Heirloom set, but we'll have to wait and see to find out. As of right now, Respawn hasn't outlined an exact date for the changes being implemented, but it could launch alongside the System Overdrive Collection event, which launches March 3, the trailer for which you can see just above.