You can have more, but I recommend sticking as close to 40 cards as possible while aiming for a ratio of 24 playable cards to 16 lands, adjusting for your curve as you see fit
Whenever a land enters the battlefield under an opponent's control, if they control more lands than you, you can put a land card from your hand into play
He believes that the Skoti are more occupied with petty squabbling than ruling the realms and thinks their downfall is imminent, probably at the hands of the elves
Wizards pulled this off perfectly, giving us 900, 700, and 300 serialized versions of the same card (again with different art, and with the non-serialized, nonfoils still a difficult pull) they gave us the first 1 of 1 card in Magics history, opened by a player in Canada and famously sold to Post Malone for $2 million