They have summoning sickness, and so can only attack for a single turn, and can block (and die during combat)
Its a cheap and useful counterspell, and given the sheer amount of Legendary Creatures in most decks these days, its not the biggest deal to sometimes pay this additional cost
P/T Set Number 365 Language Espaol Legal Formats Alchemy, Brawl, Commander, Competitive Brawl, Historic, Legacy, Modern, Pioneer, Standard, Timeless, Vintage Rulings (6/6/2025) Once Summon: Primal Odin deals combat damage to a player and the ability granted by Summon: Primal Odin's second chapter ability triggers, it doesn't matter what happens to Summon: Primal Odin
Each Commander Deck set includes 4 ready-to-play deck of 100 Magic cards (2 Traditional Foil Legendary Creature cards, 98 nonfoil cards), a 2-card Collector Booster Sample Pack (contains 1 Traditional Foil or nonfoil special treatment card of rarity Rare or higher and 1 Traditional Foil special treatment Common or Uncommon card), 1 foil-etched Display Commander (a thick cardstock copy of the commander card with foil etched into the cards border and art), 10 double-sided tokens, 1 Helper card, 1 deck box (can hold 100 sleeved cards), 1 strategy insert, and 1 reference card