MTG Commander Legendaries in premier sets receive Planeswalker treatment
Wizards of the Coast is lowering the amount Legendary Commander creatures that appear in premier sets like Duskmourn: House of Horrors, according to Head Magic: The Gathering designer Mark “MaRo” Rosewater.
Recent visits to MTG Multiverse Planes like Bloomburrow and Duskmourn have resulted in fewer Legendary creatures in premier Standard-legal sets. The nature of both Planes made it difficult to place an abundance of Legendary creatures, and it turns out this was an intentional move made by MTG devs.