Swarmyard

A regeneration land for the vermin: Insects, Rats, Spiders, and Squirrels, the four creature types the small-and-many archetypes have always been built from. The design is a deliberate piece of tribal support hidden inside a colorless utility land, which is the whole trick. Regeneration is normally a green keyword stapled to a creature or a spell, paid for in colored mana and a card; folding it into the tap ability of a land that also makes colorless means the protection costs no slot, no card, and no commitment to a color. You get a fixing-free mana source that, on a turn it would otherwise sit idle, can shrug off a removal spell or a one-sided combat trade for one of your creatures. Its narrowness lives in the target restriction: it only ever guards four creature types, so the card is worthless outside a deck built around them and quietly excellent inside one. That same narrowness is why it has settled into a swarm-deck staple rather than a generic include. It rewards exactly the boards that flood the table with cheap bodies, where keeping a key attacker or a sacrifice engine alive through a sweeper or a profitable block is worth more than a turn of tapping for mana.