The ability to play Shatterskull Smashing as a Red-producing land - possibly untapped and on demand - might win the game
Its set in a land called Valley, inhabited by tiny creatures of all kinds, from mice to bats to, yes, squirrels
Awaken the Maelstrom Baleful Mastery Black Widow, Agile Avenger Booby Trap Consecrated Sphinx Defacing Duskmage Faerie Mastermind Fate Unraveler Infernal Offering Kederekt Parasite Leela, Sevateem Warrior Malignant Growth Mathas, Fiend Seeker Mind's Eye Mind's Eye Nekusar, the Mindrazer Norn's Decree North Pole Research Base Notion Thief Ob Nixilis Reignited Ob Nixilis, the Hate-Twisted Orcish Bowmasters Pendant of Prosperity Razorkin Needlehead Red Death, Shipwrecker Saltwater Stalwart Sapphire Charm Sazacap's Brew Scrawling Crawler Sheoldred, the Apocalypse Smothering Tithe Tataru Taru The Unagi of Kyoshi Island Thief of Existence Trouble in Pairs Underworld Dreams Wedding Ring Xyris, the Writhing Storm Zurzoth, Chaos Rider
You can transform it when it attacks, and that also gives your other legendary creatures a small Overrun effect
Short answer: it depends on why you collect (prestige vs play vs long-term resale) and what you collect (rarities, promos, graded grails)