Tawnos, Urza's Apprentice

Bracket

• B1 Exhibition — Not in the same deck as its two-card combo partner: Sands of Time
• B2 Core — Not in the same deck as its two-card combo partner: Sands of Time
• B3 Upgraded — Not in the same deck as its early two-card combo partner: Sands of Time
• B4 Optimized — allowed: No restriction beyond the banned list
• B5 cEDH — allowed: No restriction beyond the banned list

Why

• Two-card combo with Sands of Time (early with Sands of Time)

How Lotus Vault estimates a bracket

Bracket: Lotus Vault analysis, with Commander Spellbook flags

Combos

14 known combos, one of them two-card.

• Tawnos, Urza's Apprentice + Mechanized Production + Myr Battlesphere
  Produces: Win the game at the beginning of your next upkeep
  View on Commander Spellbook
• Mishra, Eminent One + Mindslaver + Lithoform Engine + Tawnos, Urza's Apprentice
  Produces: You control up to three opponents on each of their turns, Lock
  View on Commander Spellbook
• Tawnos, Urza's Apprentice + Sands of Time
  Produces: Infinite Mana during the upkeep step, Infinite untap of creatures you control, Infinite mana artifacts you control can produce during the upkeep step
  View on Commander Spellbook

Combos: Commander Spellbook

Rulings

• 2018-07-13 · Wizards of the Coast
  Tawnos's ability targets an ability that is on the stack and creates another instance of that ability on the stack. It doesn't cause any object to gain an ability.
• 2018-07-13 · Wizards of the Coast
  Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keyword abilities (such as equip) are activated abilities and will have colons in their reminder text. An activated mana ability is one that produces mana as it resolves, not one that costs mana to activate.
• 2018-07-13 · Wizards of the Coast
  If the ability is modal (that is, if it says, "Choose one —" or similar), the mode is copied and can't be changed.
• 2018-07-13 · Wizards of the Coast
  If an ability is linked to a second ability, copies of that ability are also linked to that second ability. If the second ability refers to "the exiled card," it refers to all cards exiled by the ability and the copy. For example, if Tidehollow Sculler's enters-the-battlefield ability is copied and two cards are exiled, they both return when Tidehollow Sculler leaves the battlefield.
• 2018-07-13 · Wizards of the Coast
  If the ability divides damage or distributes counters among a number of targets (for example, the ability of Verdurous Gearhulk), the division and number of targets can't be changed. If you choose new targets, you must choose the same number of targets.
• 2018-07-13 · Wizards of the Coast
  Any choices made when the ability resolves won't have been made yet when it's copied. Any such choices will be made separately when the copy resolves. If a triggered ability asks you to pay a cost (such as that of Mirrorworks), you pay that cost for the copy separately.
• 2018-07-13 · Wizards of the Coast
  Triggered abilities use the word "when," "whenever," or "at." They're often written as "[Trigger condition], [effect]." Some keyword abilities are triggered abilities and will have "when," "whenever," or "at the beginning of" in their reminder text.
• 2018-07-13 · Wizards of the Coast
  The source of the copy is the same as the source of the original ability.
• 2018-07-13 · Wizards of the Coast
  In some cases involving linked abilities, an ability requires information about "the exiled card." When this happens, the ability gets multiple answers. If these answers are being used to determine the value of a variable, the sum is used. For example, if Soul Foundry's enters-the-battlefield ability is copied, two cards are exiled. The value of X in the activation cost of Soul Foundry's other ability is the sum of the two cards' mana values. As the ability resolves, you create a token copy of each card.
• 2018-07-13 · Wizards of the Coast
  If the activated ability's cost contains a choice, such as a creature to sacrifice or a number of counters to remove, the copy uses that same information. You can't pay the cost again, even if you want to.
• 2018-07-13 · Wizards of the Coast
  An "artifact source" is a permanent, spell, or card in any zone with the card type "artifact." For example, Tawnos's ability can target a cycling ability you've activated if the discarded card is an artifact card.

Rulings: Scryfall · Wizards of the Coast