Web-slinging (You may cast this spell for if you also return a tapped creature you control to its owner's hand.)
As Arachne enters, look at an opponent's hand, then choose a card type other than creature.
Spells of the chosen type cost more to cast.
Arachne is a cheap, tempo-efficient mono-white commander that taxes a noncreature card type the moment she lands, slowing combo and control opponents while you develop a board. You curve out, use Web-slinging to bounce-and-recast her (or other ETB creatures) to re-pick the most painful card type, and grind out the game with creatures, equipment, or a tax-stax shell that punishes opponents for casting spells.
Three-mana legend with a relevant tax effect and built-in evasion/discount via Web-slinging.
Hand-peek information plus a soft stax tax that hits combo, ramp, or removal-heavy decks.
Mono-white access to the format's best tax pieces, anthems, and recursion.
Web-slinging lets her dodge removal and re-enter to re-choose the optimal card type each turn.
The tax is only and only on one card type—rarely backbreaking by itself at higher tables.
Mono-white lacks card advantage and ramp, so you can fall behind in a long grind.
Bouncing a tapped creature to cheat her in costs board tempo and works best with token/expendable bodies.
No inherent way to win without a separate offensive plan, making her a support piece more than an engine.
Premier mono-white ramp/card engine that fuels paying around your own taxes and casting big threats.
Add more cumulative tax pieces (Thalia, Lodestone Golem, Archon of Emeria, Drannith Magistrate) so Arachne's compounds into real lock pressure, and pair them with mono-white ramp/draw (Smothering Tithe, Esper Sentinel, Land Tax) to offset white's card disadvantage. Lean into either a token engine for Web-slinging fodder or an efficient Voltron package so you have a fast clock, and include flicker effects (Flickerwisp, Restoration Angel) to keep re-choosing the best card type.
Legendary Creature — Spider Human Hero
more to cast.