Thunderscape Familiar

2004-10-04 Can never affect the colored part of the cost.
2004-10-04 If a spell is both black and green, you pay {1} less, not {2} less.
2004-10-04 If this card is sacrificed to pay part of a spell's cost, the cost reduction still applies.
2004-10-04 The effect is cumulative.
2004-10-04 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.
2004-10-04 The lower cost is not optional like with some other cost reducers.
2004-10-04 This can lower the cost to zero, but not below zero.

Card is in preconstructed decks:

mtg.wtf