{T}: Add {C}. {1}: Mishra's Factory becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land. {T}: Target Assembly-Worker creature gets +1/+1 until end of turn.
Each player chooses a number of lands they control equal to the number of lands controlled by the player who controls the fewest, then sacrifices the rest. Players discard cards and sacrifice creatures the same way.
Serrated Arrows enters with three arrowhead counters on it. At the beginning of your upkeep, if there are no arrowhead counters on Serrated Arrows, sacrifice it. {T}, Remove an arrowhead counter from Serrated Arrows: Put a -1/-1 counter on target creature.