Ardavah, Deva of Integrity

Ardavah, Deva of Integrity mana cost must come from just one color. (For example, six forests)
As an additional cost of casting Ardavah, Deva of Integrity, choose a color. You can cast only spells of that color as long as Ardavah, Deva of Integrity is in play. Spells of the choosen color cost {1} less to play. If you cast a spell of another color, exile Ardavah, Deva of Integrity.
Defender, indistructible.