Legatha, Adaptive Shadow

Changeling (This card is every creature type.)
As Legatha, Adaptive Shadow enters the battlefield, choose a creature type.
Tap another untapped creature of the
chosen type: Add one mana of any colour
to your mana pool.
{w}{u}{b}{r}{g}, {t}: You may cast spells of the
chosen type without paying their mana cost until end of turn.