Cavern of Souls--Freddy's End

As Cavern of Souls (where Stiff Freddy met his demise AKA Roman's Momma's attic) enters the battlefield, choose a creature type. {t}: Gain {c}. {t}: Gain one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.
Where Stiff Freddy lay. Hungry, starving, dying and then very, very, dead, for what was probably many, MANY months."