You can have up to 15 different lesson cards in your sideboard in BO3, but that wont allow you to have any other regular sideboard cards
First, I cant speak about the price of the new-to-Magic cards, because Im still working with unrealistically high presale prices at the time of writing
Walking Ballista is the easiest payoff creature to disrupt, as the loop cannot proceed without first resolving Heliods activated ability or some similar lifelink-granting effect
And if you can, give him evasion or make him unblockable
The Top Five Secrets of Strixhaven Cards at Pro Tour: Secrets of Strixhaven Shockingly, only five new cards cracked the Sunday barrier
Given how much utility Commander decks often have in order to react to massive creatures and game-ending combos, a card with a high mana cost and additional setups like Jumbo Cactuar isn't the deadliest threat out there