Sidisi, Undead Vizier — ruling 1

A creature with exploit "exploits a creature" when the controller of the exploit ability sacrifices a creature as that ability resolves.

Sidisi, Undead Vizier — ruling 2

You choose whether to sacrifice a creature and which creature to sacrifice as the exploit ability resolves.

Sidisi, Undead Vizier — ruling 3

You can sacrifice the creature with exploit if it's still on the battlefield. This will cause its other ability to trigger.

Sidisi, Undead Vizier — ruling 4

If the creature with exploit isn't on the battlefield as the exploit ability resolves, you won't get any bonus from the creature with exploit, even if you sacrifice a creature. Because the creature with exploit isn't on the battlefield, its other triggered ability won't trigger.

Sidisi, Undead Vizier — ruling 5

You can't sacrifice more than one creature to any one exploit ability.

Sidisi, Undead Vizier : règles, fonctionnement et interactions (MTG)

Sidisi, Undead Vizier 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

Deathtouch Exploit (When this creature enters, you may sacrifice a creature.) When Sidisi exploits a creature, you may search your library for a card, put it into your hand, then shuffle.

Complete guide

Sidisi, Undead Vizier turns a creature sacrifice into a search for any card in your library. The key is that exploit and the search are separate triggered abilities, so their timing—and whether Sidisi is still on the battlefield—matters.

What Sidisi Does

Sidisi is a legendary Zombie Snake with deathtouch and exploit. Deathtouch means any nonzero combat damage she deals to a creature is lethal damage; nonzero damage she deals to a creature outside combat also causes that creature to be destroyed when state-based actions are checked. When Sidisi enters, exploit triggers. As that ability resolves, you may sacrifice one creature you control. If Sidisi exploits a creature, her other ability triggers, allowing you to search your library for any card, put it into your hand, then shuffle. The card goes to your hand, not onto the battlefield, and the ability does not require you to reveal it.

How It Resolves, Step by Step

1. Sidisi enters, and her exploit ability goes on the stack. 2. Players may respond before exploit resolves. You have not yet chosen whether to sacrifice anything or which creature to sacrifice. 3. As exploit resolves, you may sacrifice one creature you control, including Sidisi herself. Exploit does not target. 4. If you sacrifice a creature and Sidisi is still present to see that sacrifice—or is herself the creature sacrificed—her search ability triggers. That trigger goes on the stack after exploit finishes resolving. 5. Players may respond again. When the search ability resolves, you may search for a card, put it into your hand, then shuffle. Example 1 — Sacrificing Solemn Simulacrum: First, resolve Solemn Simulacrum's enters ability, optionally finding a basic land and putting it onto the battlefield tapped before shuffling. Later, cast Sidisi. When her exploit ability resolves, sacrifice Solemn Simulacrum. Its dies ability and Sidisi's search ability both trigger. Because you control both triggers, you choose their order on the stack. Put the draw trigger on top to optionally draw before searching, or put the search trigger on top to search before optionally drawing.

Common Mistakes

You cannot sacrifice more than one creature to a single exploit ability. You can also decline to sacrifice anything, in which case Sidisi's search ability does not trigger. Sacrificing Sidisi to her own exploit works: her search ability still triggers. That is different from Sidisi leaving the battlefield before exploit resolves. In that case, exploit still resolves and you may still sacrifice a creature, but Sidisi's search ability will not trigger. Once the search ability has triggered and is on the stack, removing Sidisi does not stop it. Also, opponents cannot respond between your choosing a creature and sacrificing it during exploit's resolution; they must act before exploit resolves or after it finishes.

When to Play Sidisi

Play Sidisi when finding a particular card is worth the mana and a creature sacrifice. A creature with a useful dies ability can make that sacrifice more rewarding. If you have no other creature to spare, Sidisi can sacrifice herself; if you prefer to keep her without sacrificing anything, exploit is optional. Example 2 — Roaming Throne doubles the triggers: Have Roaming Throne enter and choose Zombie, then control Solemn Simulacrum when Sidisi enters. Sidisi's exploit ability triggers twice because she is another Zombie you control. Resolve the first exploit ability and sacrifice Solemn Simulacrum, keeping Sidisi on the battlefield. Sidisi's search ability now triggers twice, again thanks to Roaming Throne, while Solemn Simulacrum's dies ability triggers once because it is not a Zombie. Put those three triggers on the stack in your chosen order, above the remaining exploit ability. Each search trigger can find a card and then shuffle, and the dies trigger can draw a card. When the remaining exploit ability eventually resolves, decline to sacrifice another creature. One sacrifice has enabled two searches and an optional draw.

Guide written with AI from the official text and rulings. Official English text prevails.

How it works : Sidisi, Undead Vizier

Original English text — Wizards of the Coast / Scryfall

#1February 25, 2015· Wizards of the Coast
A creature with exploit "exploits a creature" when the controller of the exploit ability sacrifices a creature as that ability resolves.
No other card is named in this ruling.
#2February 25, 2015· Wizards of the Coast
You choose whether to sacrifice a creature and which creature to sacrifice as the exploit ability resolves.
No other card is named in this ruling.
#3February 25, 2015· Wizards of the Coast
You can sacrifice the creature with exploit if it's still on the battlefield. This will cause its other ability to trigger.
No other card is named in this ruling.
#4February 25, 2015· Wizards of the Coast
If the creature with exploit isn't on the battlefield as the exploit ability resolves, you won't get any bonus from the creature with exploit, even if you sacrifice a creature. Because the creature with exploit isn't on the battlefield, its other triggered ability won't trigger.
No other card is named in this ruling.
#5February 25, 2015· Wizards of the Coast
You can't sacrifice more than one creature to any one exploit ability.
No other card is named in this ruling.