Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.) : Add . Target opponent gains control of this creature. (Activate only as an instant.)
Legalities
Legal
Duel
Predh
Legacy
Vintage
Commander
Premodern
Oathbreaker
Not Legal
Brawl
Penny
Future
Modern
Pauper
Alchemy
Pioneer
Explorer
Historic
Standard
Timeless
Gladiator
Oldschool
Standardbrawl
Paupercommander
Rulings
2008-04-01
Because the ability is targeted, it is not a mana ability. It can only be activated when you have priority, and goes on the stack like other non-mana abilities.