Arcum Dagsson

Bracket

• B1 Exhibition — counts toward 2 tutors (Lotus Vault house cap): Counts toward the 2 tutors allowed (Lotus Vault house cap)
• B2 Core — counts toward 2 tutors (Lotus Vault house cap): Counts toward the 2 tutors allowed (Lotus Vault house cap)
• B3 Upgraded — counts toward 4 tutors (Lotus Vault house cap): Counts toward the 4 tutors allowed (Lotus Vault house cap)
• B4 Optimized — allowed: No restriction beyond the banned list
• B5 cEDH — allowed: No restriction beyond the banned list

Why

• Nonland tutor, two at most in brackets 1–2 and four in bracket 3 (Lotus Vault house cap)

How Lotus Vault estimates a bracket

Bracket: Lotus Vault analysis, with Commander Spellbook flags

Combos

2 known combos.

• Arcum Dagsson + March of the Machines + Myr Turbine + Intruder Alarm
  Produces: Put all noncreature artifact cards from your library onto the battlefield
  View on Commander Spellbook
• Arcum Dagsson + March of the Machines + Intruder Alarm + Genesis Chamber
  Produces: Infinite untap of creatures you control, Put all noncreature artifact cards from your library onto the battlefield, Infinite mana creatures you control can produce
  View on Commander Spellbook

Combos: Commander Spellbook

Rulings

• 2020-08-07 · Wizards of the Coast
  If the target artifact creature is an illegal target by the time Arcum's ability tries to resolve, the ability won't resolve. No player searches their library. If the target is legal but not sacrificed (most likely because of an effect such as that of Sigarda, Host of Herons), its controller does search their library for a noncreature artifact card.
• 2020-08-07 · Wizards of the Coast
  Any triggered abilities that trigger when the creature is sacrificed will be put onto the stack at the same time as any triggered abilities that trigger when the noncreature artifact enters the battlefield.
• 2020-08-07 · Wizards of the Coast
  Arcum Dagsson's ability targets an artifact creature, not the player who controls it.

Rulings: Scryfall · Wizards of the Coast