You aren't playing this outside of a Madrigal deck and even there it's not doing much
Declare attackers : after attack has been declared, the attacking player chooses which creatures he wishes to attack with
A deck upgrade is just what the doctor ordered, it's only a matter of which cards have the most impact
Because fighting does not count as combat, I can even send Defiler of Faith to attack my opponent and start turning the games tide (though Ill still have 4 damage marked on my creature from the fight, so Ill probably hold it back if theres a blocker, as 1 more point of damage for the rest of the turn will kill it)
Later, Id codify this idea into what Mike Flores would deem my Philosophy of Fire, but this was one of the key moments, seeing Sylvan Library literally translate four life into a single card, and Natural Spring via Sylvan Library into two cards