Geist of the Lonely Vigil — ruling 1

Once you've attacked with Geist of the Lonely Vigil, lowering the number of card types in your graveyard won't remove it from combat.

Geist of the Lonely Vigil : règles, fonctionnement et interactions (MTG)

Geist of the Lonely Vigil 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

Defender, flying Delirium — This creature can attack as though it didn't have defender as long as there are four or more card types among cards in your graveyard.

How it works : Geist of the Lonely Vigil

Original English text — Wizards of the Coast / Scryfall

#1July 13, 2016· Wizards of the Coast
Once you've attacked with Geist of the Lonely Vigil, lowering the number of card types in your graveyard won't remove it from combat.
No other card is named in this ruling.