Vennifer, Dragon Rider

Dragon Rider (As Vennifer attacks or blocks, you
may have her ride a Dragon you control. If you do,
add that creature's power, toughness, and abilities to
Vennifer until end of combat. Only ride a creature if
it isn't in combat.)
Whenever you attack with Vennifer and at least
two or more Dragons, untap all Dragons you
control. After this phase, there is an additional
combat phase.