Adapt and Overcome An ability card that allows you to fight/evade while ignoring retaliation and vigilance
Based on the latest market prices tracked on TCG Stacked, Charmers of the Grand Circle Ultra Rare is worth about $0.34 USD

Biolume Serpent Bladecoil Serpent Bog Serpent Cryptic Serpent Deep-Sea Serpent Feed the Serpent Floodtide Serpent Frilled Sea Serpent Gearseeker Serpent Harbor Serpent Iceridge Serpent Koma, Cosmos Serpent Koma, Cosmos Serpent Kukemssa Serpent Lava Serpent Lightning Serpent Lochmere Serpent Pact of the Serpent Rite of the Serpent River Serpent Ronom Serpent Sandbar Serpent Scrapdiver Serpent Sea Serpent Serpent Assassin Serpent Generator Serpent Skin Serpent Specialist Serpent Warrior Serpent of Yawning Depths Serpent of the Endless Sea Serpent of the Pass Serpent's Gift Serpent's Pass Serpent's Soul-Jar Serpent-Blade Assailant Serpentine Serpentine Ambush Serpentine Basilisk Serpentine Curve Serpentine Kavu Serpentine Spike Shoal Serpent Shrouded Serpent Skyserpent Seeker Slinking Serpent Slipstream Serpent Sliptide Serpent Spire Serpent Steelclad Serpent Stonecoil Serpent Sword Coast Serpent Sword Coast Serpent The Serpent Society The Terror of Serpent's Pass Tolarian Serpent Turntimber, Serpentine Wood Unassuming Gelatinous Serpent Veiled Serpent Vodalian Serpent Wormhole Serpent

It also introduced the idea of effects that only happen if a card is played with madness
I do think that an aggressive red deck will exist at some point while Theros is in Standard, and when it does, all of these cards will see their price increase
Fortunately, their bigger monsters also have the ability to switch monsters into another battle position, stopping the smaller monsters from having to attack