Creeping Dread — ruling 1

When a spell or ability instructs each player to discard a card, starting with the player whose turn it is and proceeding in turn order, each player selects a card from their hand without revealing it, sets it aside, and then all of those cards are revealed and discarded at once.

Creeping Dread — ruling 2

The card types that may be shared for Creeping Dread's ability are artifact, battle, creature, enchantment, instant, kindred, land, planeswalker, and sorcery. Supertypes (such as legendary and basic) and subtypes (such as Human and Equipment) are not counted.

Creeping Dread — ruling 3

If a player has no cards in hand, that player doesn't discard a card while everyone else does. If you didn't discard a card, no player can have discarded a card that shares a card type with the card you discarded, so no player loses 3 life.

Creeping Dread — ruling 4

If an opponent discards a card that shares two card types with the card you discarded, such as an artifact creature, that player still only loses 3 life.

Creeping Dread — ruling 5

Because you consider only the characteristics of a double-faced card's front face while it's not on the battlefield, a double-faced card with different card types among its faces (such as Skin Invasion) only compares its front face to the other discarded cards.

Creeping Dread : règles, fonctionnement et interactions (MTG)

Creeping Dread 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

At the beginning of your upkeep, each player discards a card. Each opponent who discarded a card that shares a card type with the card you discarded loses 3 life. (Players reveal the discarded cards simultaneously.)

How it works : Creeping Dread

Original English text — Wizards of the Coast / Scryfall

#1April 8, 2016· Wizards of the Coast
When a spell or ability instructs each player to discard a card, starting with the player whose turn it is and proceeding in turn order, each player selects a card from their hand without revealing it, sets it aside, and then all of those cards are revealed and discarded at once.
No other card is named in this ruling.
#2April 8, 2016· Wizards of the Coast
The card types that may be shared for Creeping Dread's ability are artifact, battle, creature, enchantment, instant, kindred, land, planeswalker, and sorcery. Supertypes (such as legendary and basic) and subtypes (such as Human and Equipment) are not counted.
No other card is named in this ruling.
#3April 8, 2016· Wizards of the Coast
If a player has no cards in hand, that player doesn't discard a card while everyone else does. If you didn't discard a card, no player can have discarded a card that shares a card type with the card you discarded, so no player loses 3 life.
No other card is named in this ruling.
#4April 8, 2016· Wizards of the Coast
If an opponent discards a card that shares two card types with the card you discarded, such as an artifact creature, that player still only loses 3 life.
No other card is named in this ruling.
#5April 8, 2016· Wizards of the Coast
Because you consider only the characteristics of a double-faced card's front face while it's not on the battlefield, a double-faced card with different card types among its faces (such as Skin Invasion) only compares its front face to the other discarded cards.
No other card is named in this ruling.