Oracle

Snow Land 

T: Add C.
1S: Until end of turn, Frostwalk Bastion becomes a 2/3 Construct artifact creature. It's still a land. (S can be paid with one mana from a snow permanent.)
Whenever Frostwalk Bastion deals combat damage to a creature, tap that creature and it doesn't untap during its controller's next untap step.

Tournooi-info

Legal in: Vintage, Legacy, Modern, Commander

Officiele rulings

6/14/2019
If you turn Frostwalk Bastion into a creature but haven’t controlled it continuously since your most recent turn began, you won’t be able to activate its mana ability or attack with it.

6/14/2019
A creature dealt combat damage by Frostwalk Bastion won’t untap during its controller’s next untap step, even if it was already tapped and even if Frostwalk Bastion leaves the battlefield before then.

Decktips