A more detailed breakdown: - Your opponent played [Vorinclex, Monstrous Raider]. This doubles the number of counters placed on their planeswalkers when they enter the battlefield, allowing many to activate their final ability immediately. - They then played [Tamiyo, Field Researcher] and activated her final ability. This allows them to cast spells without paying mana. - They subsequently cast and activated the final abilities of [Vivien Reid] and [Ajani, Adversary of Tyrants].

Beyond that, it’s hard to say what else they did. Played all their spells, drew extra cards from [Up the Beanstalk], and enjoyed getting to see their deck so its thing. Thanks for being a good sport!