Deepfathom Skulker — ruling 1

Activating Deepfathom Skulker’s last ability after it’s been legally blocked won’t change or undo that block. The declare attackers step is the last time you can activate the ability and have it be effective.

Deepfathom Skulker : règles, fonctionnement et interactions (MTG)

Deepfathom Skulker 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

Devoid (This card has no color.) Whenever a creature you control deals combat damage to a player, you may draw a card. : Target creature can't be blocked this turn. ( represents colorless mana.)

How it works : Deepfathom Skulker

Original English text — Wizards of the Coast / Scryfall

#1January 22, 2016· Wizards of the Coast
Activating Deepfathom Skulker’s last ability after it’s been legally blocked won’t change or undo that block. The declare attackers step is the last time you can activate the ability and have it be effective.
No other card is named in this ruling.