For 1 black and 2 colorless, and an additional cost of exiling the Dreamthief, you get a typical black draw 1 discard 1 ability
On Earth theyd be giving up noncombatant status, but neither the (old-school) Phyrexians nor the hostile forces of post-apocalyptic Dominaria seem keen on such niceties, so why not
The cost of cards being low is important, as it allows you to get cards into play at a faster rate than your opponent, giving you the opportunity to Quest and Challenge more effectively
In a nod to the flavor of a web-slinging Dinosaur, I made room for Arachnus SpinnerArachnus Spinner which can tap an untapped Spider you control to search up Arachnus WebArachnus Web to tangle up the most threatening creature on the battlefield
OK sure, full on card draw would be better and the mana restriction is significant, but if you airbend at all, a of this artifact is perfect to replay those cards
The Commander 2017 precon decks all had commanders with the eminence ability