If you do, you can search your deck for any card and put it into your hand
If a creature's power is less than 0 when it's doubled, instead that creature gets -X/-0, where X is how much less than 0 its power is
TARKIR DRAGONSTORM: BLACK I really liked Infantry Shield in my review of the new Commander Precon cards, and this is for all intents and purposes another flavor of that effect
Why proxy it: A staple across Legacy, Vintage, and high-powered Commander
Utvara Hellkite takes things further by giving you a 6/6 flying dragon token whenever one of your dragons attacks, including your dragon tokens
This specific kind of deck is often confused with Stax (which gets its name from SmokestackSmokestack), which shares a similar goal but also has the additional goal of making people sacrifice their permanents, taking taxation to the next level