In response, I'll tap the Sentry to make the Pronghorn 4/4 and I'll play Funeral Pyre on Envelop, giving myself an 1/1 token.
Then, Rat's Feast can resolve.
You done?
Limited: 12
Handsize: 5 (4?)
In play:
(UT) Plains
(UU) Island
(U) Swamp
(UU) Forest
(U) Trained Pronghorn (1/1) [Discard a card: Prevent all damage that would be dealt to ~ this turn] 4/4
(T) Battlewise Aven (3/3) [Flying. Threshold: +1/+1 and first strike] *+1/+1 counter*
(T) Vigilant Sentry (2/2) [Threshold: ~ gets +1/+1 and has "T: Target attacking or blocking creature gets +3/+3 until end of turn."]
(S) Spirit Token (1/1) [Flying]
Graveyard: Cabal Trainee, Funeral Pyre
RFG: Nullmage Shepherd, Envelop, Ironshell Beetle, Grip of Amnesia, Browbeat, Krosan Verge
Spiderman: 9
Handsize: 6
In play
(T,T) Swamp x2
(T,T) Plains x2
(T) Mt
(T,T) Forest x2
(U) Trained Pronghorn (1/1) [Discard a card: Prevent all damage that would be dealt to ~ this turn]
(U) Battlewise Aven (2/2) [Flying. Threshold: +1/+1 and first strike]
Graveyard: Canopy Claws, Selfless Exorcist, Rat's Feast
RFG: Dwarven Scorcher, Cabal Trainee, Barbarian Bully, Battle Screech