Now if only all of the cards were like this, maybe I would finally build a Magic deck myself
The term has been loosened a little since the old days, now commonly used to refer to some cards, like Spirit of the Labyrinth, that don't necessarily adhere to the 2/2 for 2 mana ratio, but still hose specific interactions while having a relatively low cost and an aggressive statline that allows them to serve as efficient beaters in situations where their ability is not relevant
Jace Beleren Jace Reawakened Jace, Arcane Strategist Jace, Architect of Thought Jace, Cunning Castaway Jace, Ingenious Mind-Mage Jace, Memory Adept Jace, Mirror Mage Jace, Telepath Unbound Jace, Unraveler of Secrets Jace, Wielder of Mysteries Jace, the Living Guildpact Jace, the Mind Sculptor Jace, the Perfected Mind Space Beleren
Monster Manual can also be used to put an expensive permanent onto the battlefield directly
While doing so, your opponent is likely putting together a larger strategy, such as control or mill