Hexdrinker — ruling 1

Level abilities count the number of level counters on the creature. Hexdrinker starts with zero level counters. Once it has at least three but no more than seven level counters, it’s 4/4 and has protection from instants. Once it has eight or more level counters, it’s 6/6 and has protection from everything. It always has level up {1}.

Hexdrinker — ruling 2

If an effect has set Hexdrinker’s power and/or toughness to a specific value after it entered the battlefield, leveling up won’t change that characteristic.

Hexdrinker — ruling 3

Protection from instants means that Hexdrinker can’t be the target of instant spells or abilities from instant cards (such as an ability of an instant card that triggers when that card is cycled), and all damage that an instant spell or instant card would deal to it is prevented. Nothing other than these events is prevented or illegal.

Hexdrinker — ruling 4

Protection from everything means that Hexdrinker can’t be the target of any spells or abilities, it can’t be blocked, nothing can be attached to it, and all damage that would be dealt to it is prevented. It can still be affected in other ways (such as by Winds of Abandon cast for its overload cost, for example).

Hexdrinker : règles, fonctionnement et interactions (MTG)

Hexdrinker 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

Level up (: Put a level counter on this. Level up only as a sorcery.) LEVEL 3-7 4/4 Protection from instants LEVEL 8+ 6/6 Protection from everything

How it works : Hexdrinker

Original English text — Wizards of the Coast / Scryfall

#1June 14, 2019· Wizards of the Coast
Level abilities count the number of level counters on the creature. Hexdrinker starts with zero level counters. Once it has at least three but no more than seven level counters, it’s 4/4 and has protection from instants. Once it has eight or more level counters, it’s 6/6 and has protection from everything. It always has level up .
No other card is named in this ruling.
#2June 14, 2019· Wizards of the Coast
If an effect has set Hexdrinker’s power and/or toughness to a specific value after it entered the battlefield, leveling up won’t change that characteristic.
No other card is named in this ruling.
#3June 14, 2019· Wizards of the Coast
Protection from instants means that Hexdrinker can’t be the target of instant spells or abilities from instant cards (such as an ability of an instant card that triggers when that card is cycled), and all damage that an instant spell or instant card would deal to it is prevented. Nothing other than these events is prevented or illegal.
No other card is named in this ruling.
#4June 14, 2019· Wizards of the Coast
Protection from everything means that Hexdrinker can’t be the target of any spells or abilities, it can’t be blocked, nothing can be attached to it, and all damage that would be dealt to it is prevented. It can still be affected in other ways (such as by Winds of Abandon cast for its overload cost, for example).
No other card is named in this ruling.