The Seventh Doctor card, showing Slyvester McCoy as the Doctor, features a much more complicated ability that has defending players attempting to guess whether the mana value of a card in the attacking players hand is greater than the number of artifacts they control
Only tournament judges received these cards, which means they were not available in starter packs or booster, leading to a lower supply
The card advantage and removal packed into one trigger make equipment like this a staple in many competitive decks
All that said, the bonus here is nice
Serra was a powerful Planeswalker who came to Dominaria thousands of years before the events of Dominaria United, explains Roy Graham, Game Designer: Story
It's one of the strongest Izzet commanders ever printed thanks to generating ridiculous amount of mana and looping spells for game-winning combos