Gwyra the Crimson Dusk

If it's neither day nor night, it becomes day as
Gwyra the Crimson Dusk enters the battlefield.
As long as its day Gwyra the Crimson Dusk has defender and lifelink.
As long as its night Gwyra the Crimson Dusk has flying and deathtouch.
When Gwyra the Crimson Dusk dies, if its night, return it to its owners hand.