Legendary Creature — Beholder

Xanathar, Guild Kingpin

Mana value6EDHREC#6,456

Build with Wyrm Build manually Card details

The Commander

At the beginning of your upkeep, choose target opponent. Until end of turn, that player can't cast spells, you may look at the top card of their library any time, you may play the top card of their library, and you may spend mana as though it were mana of any color to cast spells this way.

Guide

Gameplan

Lock one opponent out of casting each turn while plundering the top of their library, grinding incremental card advantage and tempo. You play a UB control shell with removal, stax, and theft effects, locking the table down and eventually winning with value engines or a finisher. Xanathar wants you to attack the social dynamics: shut down the biggest threat each upkeep.

Strengths

Repeatable per-turn lockdown of an opponent's casting, neutralizing combo and control players
Free card advantage by playing off the top of a chosen opponent's library with any color mana
Lives in the best control colors for counters, removal, and card draw
Synergizes with other 'can't cast spells' and stax effects to broaden the lock

Weaknesses

Only stops one opponent per upkeep, so a three-opponent table can still race or combo around you
Six mana and dies easily to removal, resetting your engine
Doesn't generate a fast clock on its own and games can drag
Vulnerable to activated abilities, mana abilities, and permanents already on board

Key Cards

Notion Thief — Turns opponents' draw effects into your cards, multiplying the value of denying their turn.
Knowledge Pool — Combines with Xanathar so your locked opponent literally cannot cast anything from exile.
Teferi, Mage of Zhalfir — Forces sorcery-speed casting, tightening the noose alongside Xanathar's restriction.
Mystic Remora — Cheap, repeatable card advantage that fuels a grindy control game.
Cyclonic Rift — The premier blue blowout that lets you finally close after establishing control.

Upgrade Path

Lean harder into the stax angle with Drannith Magistrate, Grand Arbiter Augustin IV, and Archmage's Charm to broaden the lockdown beyond one player. Add fast mana (Mana Crypt, Sol Ring, Talismans) so Xanathar lands earlier and you can hold up interaction, and round out with a tutorable finisher like Thassa's Oracle plus Demonic Consultation for a compact wincon.

Core Cards

The most-played cards for this commander, built from aggregated deck data (the Mythic Graph). Build public decks to seed it.

Win Conditions

▸Grind everyone out of resources, then win with a value engine or commander damage
▸Cast a big finisher or wrath like Cyclonic Rift and swing with whatever sticks
▸Assemble a soft-lock (Knowledge Pool, Teferi) and win uncontested over time
▸Mill or theft-based attrition closing out a stalled board

Archetypes

Control — Xanathar denies casting and feeds you cards, the backbone of a UB lock-and-grind plan.
Stax — Pairs with 'can't cast' and resource-denial pieces to extend lockdown across the table.
Theft — Playing off opponents' libraries dovetails with broader steal-everything strategies.
Spellslinger — A counter-and-removal-heavy build leverages Xanathar to protect your engine.