Ridged Regisaur

Trample, reach
Ridged Regisaur's toughness doesn't increase
from its Rider ability. Instead, its power increases
by an amount equal to the power of the creature
riding it.
Rider 3 (This creature can't attack unless you tap an
untapped nonmount creature you control with
toughness 1 or more. Then, this creature's toughness
increases by an amount equal to the tapped creature's
toughness.)