Abattoir Ghoul — ruling 1

You'll gain life equal to the creature's last known toughness before it died. For example, if Abattoir Ghoul deals 3 first-strike damage to a 7/7 creature and then you give the creature -5/-5 before the regular combat damage step, you'll gain 2 life.

Abattoir Ghoul : règles, fonctionnement et interactions (MTG)

Abattoir Ghoul 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

First strike Whenever a creature dealt damage by this creature this turn dies, you gain life equal to that creature's toughness.

How it works : Abattoir Ghoul

Original English text — Wizards of the Coast / Scryfall

#1September 22, 2011· Wizards of the Coast
You'll gain life equal to the creature's last known toughness before it died. For example, if Abattoir Ghoul deals 3 first-strike damage to a 7/7 creature and then you give the creature -5/-5 before the regular combat damage step, you'll gain 2 life.
No other card is named in this ruling.