Emry, Lurker of the Loch — ruling 1

You'll still pay all costs for a spell cast this way, including additional costs. You may also pay alternative costs if any are available.

Emry, Lurker of the Loch — ruling 2

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Emry). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.

Emry, Lurker of the Loch — ruling 3

Once you announce that you're casting a spell, no player may take actions until the spell has been paid for. Notably, opponents can't try to change by how much Emry's cost is reduced.

Emry, Lurker of the Loch — ruling 4

Casting the target card causes it to leave your graveyard and become a new object. You can't cast it again if it returns to your graveyard this turn.

Emry, Lurker of the Loch — ruling 5

If Emry's last ability targets an artifact land card, you can't play it. Effects that allow you to "cast" a card don't allow you to play a land card.

Emry, Lurker of the Loch — ruling 6

The cost reduction ability reduces only the generic mana in Emry's cost. The colored mana must still be paid.

Emry, Lurker of the Loch — ruling 7

You must follow the normal timing permissions and restrictions for the target artifact card. Unless it has flash, you'll most likely only be able to cast it during your main phase while the stack is empty.

Emry, Lurker of the Loch : règles, fonctionnement et interactions (MTG)

Emry, Lurker of the Loch 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

Affinity for artifacts (This spell costs less to cast for each artifact you control.) When Emry enters, mill four cards. : Choose target artifact card in your graveyard. You may cast that card this turn. (You still pay its costs. Timing rules still apply.)

How it works : Emry, Lurker of the Loch

Original English text — Wizards of the Coast / Scryfall

#1October 4, 2019· Wizards of the Coast
You'll still pay all costs for a spell cast this way, including additional costs. You may also pay alternative costs if any are available.
No other card is named in this ruling.
#2October 4, 2019· Wizards of the Coast
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Emry). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
No other card is named in this ruling.
#3October 4, 2019· Wizards of the Coast
Once you announce that you're casting a spell, no player may take actions until the spell has been paid for. Notably, opponents can't try to change by how much Emry's cost is reduced.
No other card is named in this ruling.
#4October 4, 2019· Wizards of the Coast
Casting the target card causes it to leave your graveyard and become a new object. You can't cast it again if it returns to your graveyard this turn.
No other card is named in this ruling.
#5October 4, 2019· Wizards of the Coast
If Emry's last ability targets an artifact land card, you can't play it. Effects that allow you to "cast" a card don't allow you to play a land card.
No other card is named in this ruling.
#6October 4, 2019· Wizards of the Coast
The cost reduction ability reduces only the generic mana in Emry's cost. The colored mana must still be paid.
No other card is named in this ruling.
#7October 4, 2019· Wizards of the Coast
You must follow the normal timing permissions and restrictions for the target artifact card. Unless it has flash, you'll most likely only be able to cast it during your main phase while the stack is empty.
No other card is named in this ruling.