Gaining life (and putting out blockers) are two of the most surefire ways to deal with aggro decks, and the Ferocidon puts the breaks on both, leaving opponents rather helpless
It's been reported that a copy of the ultra-rare card just sold for four million USD on eBay
However, apart from the official rule terminology in Pokmon TCG, there are quite a few expressions and slang terms specific to the card game community and the Pokmon TCG community

A Most Helpful Weaver Aetheric Amplifier Ajani Fells the Godsire Ajani, Caller of the Pride Aragorn, Hornburg Hero Arcade Cabinet Arna Kennerd, Skycaptain Ascendant Acolyte Aven Sunstriker Avenging Huntbonder Border Guardian Bright-Palm, Soul Awakener Bristly Bill, Spine Sower Bronze Guardian Byrke, Long Ear of the Law Champions of Tyr Cren of the Spider Brood Cyan, Vengeful Samurai Death-Greeter's Champion Deepglow Skate Disciplined Duelist Dragonsguard Elite Dual-Sun Technique Evolution Vat Fabled Hero Fangs of Kalonia Fearless Skald Ferrafor, Young Yew Firja's Retribution Game of Chaos Gavel of the Righteous Gilder Bairn Gimli of the Glittering Caves Growth Curve Hound of Griselbrand Hulk, Strongest There Is Hydra's Growth Illuminator Virtuoso Indominus Rex, Alpha Invigorating Surge Jawbone Duelist Jenny, Generated Anomaly Kalemne, Disciple of Iroas Kamiz, Obscura Oculus Kathril, Aspect Warper Kayla's Command Kinjalli's Dawnrunner Knighted Myr Leonardo, Sewer Samurai Level Up Lily Bowen, Raging Grandma Luxior, Ignited (playtest) Mai, Jaded Edge Markov Blademaster Mockingbird, Ace Agent Momentum Rumbler Mossborn Hydra Okoye, Mighty and Adored Origin of Spider-Man Ornery Tumblewagg Overclocked Electromancer Pacesetter Paragon Paradox Zone Practiced Offense Quest for Pure Flame Quicksilver, Brash Blur Rayami, First of the Fallen Rediscover the Way Roar of Endless Song Roar of the Fifth People Sage of the Fang Savageborn Hydra

That means, to get all three, you must play in both days of the Casual Play, and then also take part in the Willpower League
You can cast it during an opponents upkeep to prevent their sorcery-speed spells