This Is a cool combo to use in order to get 2 creatures of the same power toughness and abilities (they're just different colors).

Heres how it goes:

1.You play either a Penumbra Wurm, Kavu, Bobcat or any others.
2. Let it go into your graveyard (best from combat or another creatures ability, not sacrifice). You will then have a token identical to the penumbra you had in play (cept it will be black, not green).
3. You then use a raise dead, Urborg uprising, Recover or anything that can bring your creature from your graveyard to your hand (use it on the Penumbra).
4. Play the regenerated creature. You will then have two of the same creature in play.