Zndrsplt, Eye of Wisdom + Okaun, Eye of Chaos I mean, we do have a Secret Lair, full precon called Heads I Win, Tails You Lose with these two chaos commanders at the helm
Speculation Kapow
Given that an international fast-food company is carrying it (and this is just one of the current Pokemon TCG promos going on), its not rare either
Chittering Harvester Significant value for the five mana, most of the time getting a three-for-nothing

Aesi, Tyrant of Gyre Strait Benthic Anomaly Benthic Behemoth Biolume Egg Biolume Serpent Bladecoil Serpent Bog Serpent Caetus, Sea Tyrant of Segovia Cryptic Serpent Deep-Sea Serpent Deep-Sea Terror Denizen of the Deep Dirgur Nemesis Dreamwinder Floodtide Serpent Frilled Sea Serpent Gearseeker Serpent Harbor Serpent Iceridge Serpent Junk Winder Koma, Cosmos Serpent Koma, Cosmos Serpent Koma, World-Eater Kukemssa Serpent Lava Serpent Lightning Serpent Loch Mare Lochmere Serpent Marjhan River Serpent Ronom Serpent Sandbar Serpent Scrapdiver Serpent Sea Monster Sea Serpent Serpent of Yawning Depths Serpent of the Endless Sea Serpent of the Pass Shoal Serpent Shrouded Serpent Slinking Serpent Slipstream Serpent Sliptide Serpent Spire Serpent Steelclad Serpent Striped Riverwinder Sword Coast Serpent Taniwha The Terror of Serpent's Pass The Unagi of Kyoshi Island Tolarian Serpent Tolarian Terror Verazol, the Split Current Vodalian Serpent Wormhole Serpent Xolatoyac, the Smiling Flood Yorion, Sky Nomad

Kyle Massa doesnt even use 600 as a baseline anymore