Mizzium Meddler — ruling 1

If changing one target of a spell or ability to Mizzium Meddler would make other targets of that spell or ability illegal, the targets remain unchanged.

Mizzium Meddler — ruling 2

If the spell or ability has multiple instances of the word “target,” you choose which target you’re changing to Mizzium Meddler as Mizium Meddler’s ability resolves.

Mizzium Meddler — ruling 3

The target of the spell or ability won’t change unless Mizzium Meddler fulfills all the targeting criteria. If a spell or ability has multiple targets, such as Send to Sleep, you can change only one of the targets to Mizzium Meddler.

Mizzium Meddler — ruling 4

If a spell or ability has a variable number of targets, you can’t change the number of targets.

Mizzium Meddler — ruling 5

If Mizzium Meddler leaves the battlefield before its ability resolves, the targets remain unchanged.

Mizzium Meddler — ruling 6

Mizzium Meddler’s triggered ability can target a spell or ability even if Mizzium Meddler wouldn’t be a legal target for that spell or ability. However, the target of that spell or ability will remain unchanged.

Mizzium Meddler — ruling 7

If Mizzium Meddler’s triggered ability targets a spell or ability with no targets, nothing happens.

Mizzium Meddler : règles, fonctionnement et interactions (MTG)

Mizzium Meddler is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Flash (You may cast this spell any time you could cast an instant.) When this creature enters, you may change a target of target spell or ability to this creature.

How it works : Mizzium Meddler

Original English text — Wizards of the Coast / Scryfall

#1June 22, 2015· Wizards of the Coast
If changing one target of a spell or ability to Mizzium Meddler would make other targets of that spell or ability illegal, the targets remain unchanged.
No other card is named in this ruling.
#2June 22, 2015· Wizards of the Coast
If the spell or ability has multiple instances of the word “target,” you choose which target you’re changing to Mizzium Meddler as Mizium Meddler’s ability resolves.
No other card is named in this ruling.
#3June 22, 2015· Wizards of the Coast
The target of the spell or ability won’t change unless Mizzium Meddler fulfills all the targeting criteria. If a spell or ability has multiple targets, such as Send to Sleep, you can change only one of the targets to Mizzium Meddler.
No other card is named in this ruling.
#4June 22, 2015· Wizards of the Coast
If a spell or ability has a variable number of targets, you can’t change the number of targets.
No other card is named in this ruling.
#5June 22, 2015· Wizards of the Coast
If Mizzium Meddler leaves the battlefield before its ability resolves, the targets remain unchanged.
No other card is named in this ruling.
#6June 22, 2015· Wizards of the Coast
Mizzium Meddler’s triggered ability can target a spell or ability even if Mizzium Meddler wouldn’t be a legal target for that spell or ability. However, the target of that spell or ability will remain unchanged.
No other card is named in this ruling.
#7June 22, 2015· Wizards of the Coast
If Mizzium Meddler’s triggered ability targets a spell or ability with no targets, nothing happens.
No other card is named in this ruling.