Untap, Upkeep, Draw
Play priest of titania.
Tap Priest of titania for 4 mana, play Heedless one (6/6(5 elves + +1/+1 from elvish champion.
Attack with Llanowar Elves x2 + Elvish Champion + Heedless One.
Whatever happens, I'm tapped out and have no hand cards, so you can go after blocking.
BPC: 20
Hand: 0
Library: 51
In Play:
(TT) Forest x2
Concordant crossroads (Creatures can attack or use abilities that include tap in the activation cost as soon as they come into play on their controller's side.)
Steely resolve (Enchantment green; creature type of choice gets shroud. I choose elves.)
(T) Llanowar elves (1/1 green tap: G to pool)
(T) Llanowar elves (1/1 green tap: G to pool)
(T) Elvish Champion (2/2 Elf, Other elves get +1/+1 and Forestwalk)
(T) Priest of TitaniaT) (1/1 green, Tap: G to pool for each elf in play)
(T) Heedless OneT) (*/* green, power and toughness equal to the number of elves in play, so now 6/6, Trample.)
Graveyard:
RFG:
MM: 14
Hand: 5
Library: 50
In Play:
(UT) Mountain x2
(T) Badlands (T:R or B)
(U) Bola Warrior Spellshaper (1/1, R, T, Discard a card from your hand: Target creature can't block this turn.)
(S) Apprentice Necromancer Wizard (1/1, B, tap, Sacrifice Apprentice Necromancer: Return target creature card from your graveyard to play. That creature gains haste. At end of turn, sacrifice it.)
Graveyard: