Underdark Explorer — ruling 1

The initiative is a designation a player can have. A player with the initiative designation is said to “have the initiative.” The initiative carries two inherent rules. First, whenever a player takes the initiative, and at the beginning of the upkeep of the player with the initiative, that player ventures into Undercity. Second, whenever one or more creatures a player controls deal combat damage to the player who has the initiative, the first player takes the initiative. Also, some abilities will refer to having the initiative and provide other benefits.

Underdark Explorer — ruling 2

There is no initiative in a game until an effect instructs a player to take the initiative. Once a player is instructed to do this, they have the initiative until another player takes the initiative.

Underdark Explorer — ruling 3

Only one player can have the initiative at a time. As one player takes the initiative, any other player that had the initiative ceases to have it.

Underdark Explorer — ruling 4

A player who currently has the initiative may take the initiative again. This causes that player to venture into Undercity again, but does not cause them to have multiple initiative designations.

Underdark Explorer — ruling 5

If the player with the initiative leaves the game, the active player takes the initiative at the same time that player leaves the game. If the active player is leaving the game or if there is no active player, the next player in turn order takes the initiative.

Underdark Explorer — ruling 6

In a Two-Headed Giant game, if both players on a team deal combat damage to the player that has the initiative at the same time, the player with the initiative will choose the order of the triggered abilities. Then, as those abilities resolve, one team member takes the initiative (and ventures into Undercity) and then the other team member does the same. The last player to take the initiative keeps it until the initiative changes again.

Underdark Explorer — ruling 7

You cannot venture into Undercity unless instructed to do so, either because you have the initiative at the beginning of your upkeep or because you take the initiative. Notably, if you aren’t in a dungeon and an effect instructs you to venture into the dungeon (not venture into Undercity), you can’t start Undercity.

Underdark Explorer — ruling 8

Similarly, when instructed to venture into Undercity, you can’t start a dungeon that isn’t Undercity.

Underdark Explorer : règles, fonctionnement et interactions (MTG)

Underdark Explorer 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

Menace (This creature can't be blocked except by two or more creatures.) When this creature enters, you take the initiative.

How it works : Underdark Explorer

Original English text — Wizards of the Coast / Scryfall

#1June 10, 2022· Wizards of the Coast
The initiative is a designation a player can have. A player with the initiative designation is said to “have the initiative.” The initiative carries two inherent rules. First, whenever a player takes the initiative, and at the beginning of the upkeep of the player with the initiative, that player ventures into Undercity. Second, whenever one or more creatures a player controls deal combat damage to the player who has the initiative, the first player takes the initiative. Also, some abilities will refer to having the initiative and provide other benefits.
No other card is named in this ruling.
#2June 10, 2022· Wizards of the Coast
There is no initiative in a game until an effect instructs a player to take the initiative. Once a player is instructed to do this, they have the initiative until another player takes the initiative.
No other card is named in this ruling.
#3June 10, 2022· Wizards of the Coast
Only one player can have the initiative at a time. As one player takes the initiative, any other player that had the initiative ceases to have it.
No other card is named in this ruling.
#4June 10, 2022· Wizards of the Coast
A player who currently has the initiative may take the initiative again. This causes that player to venture into Undercity again, but does not cause them to have multiple initiative designations.
No other card is named in this ruling.
#5June 10, 2022· Wizards of the Coast
If the player with the initiative leaves the game, the active player takes the initiative at the same time that player leaves the game. If the active player is leaving the game or if there is no active player, the next player in turn order takes the initiative.
No other card is named in this ruling.
#6June 10, 2022· Wizards of the Coast
In a Two-Headed Giant game, if both players on a team deal combat damage to the player that has the initiative at the same time, the player with the initiative will choose the order of the triggered abilities. Then, as those abilities resolve, one team member takes the initiative (and ventures into Undercity) and then the other team member does the same. The last player to take the initiative keeps it until the initiative changes again.
No other card is named in this ruling.
#7June 10, 2022· Wizards of the Coast
You cannot venture into Undercity unless instructed to do so, either because you have the initiative at the beginning of your upkeep or because you take the initiative. Notably, if you aren’t in a dungeon and an effect instructs you to venture into the dungeon (not venture into Undercity), you can’t start Undercity.
No other card is named in this ruling.
#8June 10, 2022· Wizards of the Coast
Similarly, when instructed to venture into Undercity, you can’t start a dungeon that isn’t Undercity.
No other card is named in this ruling.
#9June 10, 2022· Wizards of the Coast
If you aren’t in a dungeon when instructed to venture into Undercity, you will put Undercity into the command zone and move your venture marker to Secret Entrance (the first room).
No other card is named in this ruling.
#10June 10, 2022· Wizards of the Coast
If you’re already in a dungeon when instructed to venture into Undercity, you move to the next room of that dungeon. If you are already in the last room, you will complete that dungeon and start Undercity. This is true whether you’re already in Undercity or any other dungeon.
No other card is named in this ruling.