Unwinding Clock

Bracket

• B1 Exhibition — allowed: No restriction at this bracket
• B2 Core — allowed: No restriction at this bracket
• B3 Upgraded — allowed: No restriction at this bracket
• B4 Optimized — allowed: No restriction beyond the banned list
• B5 cEDH — allowed: No restriction beyond the banned list

Why

• No Game Changer, mass land denial, extra turn, tutor or two-card combo

How Lotus Vault estimates a bracket

Bracket: Lotus Vault analysis, with Commander Spellbook flags

Combos

5 known combos.

• Nevinyrral's Disk + Darksteel Forge + Mycosynth Lattice + Unwinding Clock
  Produces: Destroy all permanents opponents control each turn, Lock, Mass Land Denial
  View on Commander Spellbook
• Kill Switch + Mycosynth Lattice + Unwinding Clock
  Produces: Permanents your opponents control do not untap, Lock, Mass Land Denial
  View on Commander Spellbook
• Emrakul, the Promised End + Erratic Portal + Unwinding Clock + Vedalken Orrery
  Produces: Infinite turns for each opponent, You control your opponents on each of their turns, Lock
  View on Commander Spellbook

Combos: Commander Spellbook

Rulings

• 2011-06-01 · Wizards of the Coast
  Those artifacts untap at the same time as the active player's permanents. You have no choice about what untaps and can't choose to not untap an artifact you control.
• 2011-06-01 · Wizards of the Coast
  Even if you control more than one Unwinding Clock, you'll only untap your artifacts once during each other player's untap step.
• 2011-06-01 · Wizards of the Coast
  Some effects, such as the one generated by Rust Tick's ability, state that an artifact doesn't untap during its controller's untap step. These effects won't apply and stop the artifact from untapping during another player's untap step.

Rulings: Scryfall · Wizards of the Coast