Card

Mox Amber

Mana cost {0}

{T}: Add one mana of any color among legendary creatures and planeswalkers you control.

Part of 83 known combos, 2 of them two-card. 3 official rulings.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partners: Hullbreaker Horror, Tidespout Tyrant
B2 Core — Not in the same deck as its two-card combo partners: Hullbreaker Horror, Tidespout Tyrant
B3 Upgraded — Not in the same deck as its early two-card combo partner: Hullbreaker Horror
B4 Optimized — allowed: No restriction beyond the banned list
B5 cEDH — allowed: No restriction beyond the banned list

Two-card combo with Hullbreaker Horror, Tidespout Tyrant (early with Hullbreaker Horror)

Bracket: Lotus Vault analysis, with Commander Spellbook flags

83 known combos, 2 of them two-card.

Hullbreaker Horror + Mox Amber
Produces: Infinite creature ETB, Infinite creature LTB, Infinite colored mana
View on Commander Spellbook
Teferi, Time Raveler + Displacer Kitten + Mox Amber
Produces: Infinite card draw, Infinite draw triggers, Near-infinite mana among colors of legendary creatures and planeswalkers you control
View on Commander Spellbook
Tidespout Tyrant + Mox Amber
Produces: Infinite storm count
View on Commander Spellbook

2018-04-27 · Wizards of the Coast
If you control no legendary creatures or legendary planeswalkers, you can activate Mox Amber's ability, but you won't add any mana.
2018-04-27 · Wizards of the Coast
Mox Amber's ability adds one mana of the color of your choice from among the colors of legendary creatures and legendary planeswalkers you control. It doesn't add one mana of each of those colors.
2018-04-27 · Wizards of the Coast
If your legendary creatures and legendary planeswalkers are all colorless, you can activate Mox Amber's ability, but you won't add any mana. Colorless is not a color.

Rulings: Scryfall · Wizards of the Coast