Scion of the Ur-Dragon | Skithiryx, the Blight Dragon | Moltensteel Dragon

Cards

Scion of the Ur-Dragon on the battlefield.
Skithiryx and
Moltensteel Dragon in your library.
An opponent is unable to block and kill
Scion of the Ur-Dragon.
({4} magic symbol) ({RP} magic symbol) ({RP} magic symbol) ({RP} magic symbol) ({RP} magic symbol) ({RP} magic symbol) ({RP} magic symbol) , plus an additional ({B} magic symbol) if
Scion of the Ur-Dragon has summoning sickness available.

Activate
Scion of the Ur-Dragon by paying ({2} magic symbol) .
Holding priority, activate
Scion of the Ur-Dragon a second time by paying ({2} magic symbol) .
Resolve the first
Scion of the Ur-Dragon ability, searching your library for
Moltensteel Dragon, putting it into your graveyard, causing
Scion of the Ur-Dragon to become a copy of
Moltensteel Dragon until end of turn, and shuffling your library.
Activate
Scion of the Ur-Dragon by paying ({RP} magic symbol) , giving itself +1/+0 until end of turn.
Repeat step 4 five additional times.
Resolve the
Scion of the Ur-Dragon ability from step 1, searching your library for
Skithiryx, putting it into your graveyard, causing
Scion of the Ur-Dragon to become a copy of
Skithiryx until end of turn, and shuffling your library.
If
Scion of the Ur-Dragon has summoning sickness, activate it by paying ({B} magic symbol) , giving it haste until end of turn.
Deal combat damage with
Scion of the Ur-Dragon, causing an opponent to get ten poison counters and lose the game due to lethal infect damage.