Thornscape Familiar

• WWizards of the Coast2004-10-04
  Official Ruling
  If a spell is both red and white, you pay less, not less.
• WWizards of the Coast2004-10-04
  Official Ruling
  Can never affect the colored part of the cost.
• WWizards of the Coast2004-10-04
  Official Ruling
  If this card is sacrificed to pay part of a spell’s cost, the cost reduction still applies.
• WWizards of the Coast2004-10-04
  Official Ruling
  This can lower the cost to zero, but not below zero.
• WWizards of the Coast2004-10-04
  Official Ruling
  The effect is cumulative.
• WWizards of the Coast2004-10-04
  Official Ruling
  The lower cost is not optional like with some other cost reducers.
• WWizards of the Coast2004-10-04
  Official Ruling
  The generic X cost is still considered generic even if there is a requirement that a specific color be used for it. For example, “only black mana can be spent this way”. This distinction is important for effects which reduce the generic portion of a spell’s cost.

Rulings via Scryfall