Chartooth Cougar

You can choose to find any card with the Mountain land type, including nonbasic lands. You can also choose not to find a card, even if there is a Mountain card in your library.

Unlike the normal cycling ability, Mountaincycling doesn't allow you to draw a card. Instead, it lets you search your library for a Mountain card. After you find a Mountain card in your library, you reveal it, put it into your hand, then shuffle your library.

Mountaincycling is a form of cycling. Any ability that triggers on a card being cycled also triggers on Mountaincycling this card. Any ability that stops a cycling ability from being activated also stops Mountaincycling from being activated.