You may cast the copy by paying 3 rather than paying its mana cost." Equipped creature gets +0/+2, is a Wizard in addition to its other types, and has "Whenever this creature attacks, exile up to one target instant or sorcery card from defending player's graveyard
4 - Number 41: Bagooska the Terribly Tired Tapir Even though it is a bit unpopular nowadays, Number 41: Bagooska the Terribly Tired Tapir has been, historically, powerful, particularly in formats in which the main decks don't use link monsters
Peer into the Abyss can just kill an opponent if their deck is thick enough
So far in Arena 's short life, Wizards has shown itself to be completely unwilling to really support any format outside of Standard and bot-based Limited
There is of course also Emry, Lurker of the Loch, who has a discount based on the number of artifacts you control
Not all artifacts are colorless, though, and the best colorless artifacts are good enough to be powerhouses everywhere