What matchmaking for onyx lancer?

I have pretty much every onyx skin but the lancer, what do I have to be onyx in to acquire the onyx lancer?

None. Season 4 gives , the Gnasher, Markza Mk.1, Longshot, Boltok and Snub. Highest rank, any playlist.
https://gearsofwar.com/en-us/community/whatsup-may17-2018

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