4 Oct 2019
Once the common lands (such as Mystic Sanctuary) enter the battlefield tapped, there's no way to untap them with a spell or ability to make their last ability trigger.
4 Oct 2019
The mana generated by Castle Garenbrig's last ability can't be spent to activate abilities of creature cards that aren't on the battlefield.
4 Oct 2019
Although the common lands have basic land types, they aren't basic lands.