Replacement Order: You Choose
Judge Level 1Doubling and adding — the right order turns 6 counters into 8.
Cards involved
Two amplifiers
You control Corpsejack Menace ("If one or more counters would be put on a permanent you control, twice that many are put on it instead") and Master Biomancer (2/4: "Each creature enters with additional +1/+1 counters equal to his power"). You cast Walking Ballista with X=2.
What happens?
Both effects want to modify the event.
Who determines the order — and what is the maximum number of counters?
Pick an answer to continue.
If multiple replacement effects want to modify the same event, the affected player or the controller of the affected object chooses the order (616.1). Here it genuinely matters: +2 then ×2 = 8; the other way around only 2×2+2 = 6.
616.1If two or more replacement and/or prevention effects are attempting to modify the way an event affects an object or player, the affected object’s controller (or its owner if it has no controller) or the affected player chooses one to apply, following the steps listed below. If two or more players have to make these choices at the same time, choices are made in APNAP order (see rule 101.4).
The Ballista lands
You apply Biomancer first, then Corpsejack: Walking Ballista enters as an 8/8.
616.1If two or more replacement and/or prevention effects are attempting to modify the way an event affects an object or player, the affected object’s controller (or its owner if it has no controller) or the affected player chooses one to apply, following the steps listed below. If two or more players have to make these choices at the same time, choices are made in APNAP order (see rule 101.4).
Rule of thumb
With replacement chains, always ask: whose event is being replaced? That person (or the object's controller) chooses — not the timestamp, not the active player.
616.1If two or more replacement and/or prevention effects are attempting to modify the way an event affects an object or player, the affected object’s controller (or its owner if it has no controller) or the affected player chooses one to apply, following the steps listed below. If two or more players have to make these choices at the same time, choices are made in APNAP order (see rule 101.4).
Stack
Corpsejack Menace
Counters on your permanents are doubled
Master Biomancer
Your creatures enter with +2 additional counters
Walking Ballista
Enters with X counters — X=2
The stack is empty.
Battlefield
—