Does Antimagic Field suppress or prevent petrification from a creature ability?

Question

Inspired by this question and in particular, this answer. I'm focusing on a specific effect; petrification.

If by a medusa's gaze or a beholder's eye rays (or other creatures with a similar ability), their abilities give you precisely two chances; the initial save, which if you fail will restrain you as you begin to turn to stone, then a final save, which if you fail again sees you petrified.

From this, I have a couple of closely related questions with regards to how this method of petrification interacts with antimagic field (I decided to split this question up into two sets, since otherwise all 5 questions together made this post too broad; the other set of questions is here):

• If a creature has been petrified by a creature, as in failed both saves, does antimagic field have any effect on their petrified condition?
• If a creature is currently being petrified, meaning they've failed one save but have yet to make the other save, does antimagic field stop the magical effect and they effectively auto-succeed that second saving throw?

Answer 1

The Petrified Condition would not be suppressed or removed unless it is magical

Antimagic field has a specific list of effects stating what it is capable of doing - and the one most applicable to this situation would be:

Targeted Effects. Spells and other magical effects, such as magic missile and charm person, that target a creature or an object in the sphere have no effect on that target.

Petrified is neither a Spell effect or a Magic effect, but a condition, similar to being grappled or exhausted.

If you wanted to remove petrification, you need to use a spell that specifically states it is capable of doing so. For example, the spell Greater Restoration:

You can reduce the target's exhaustion level by one, or end one of the following effects on the target:

• One effect that charmed or petrified the target

However, when the effect is applied by a Beholders eye rays, it is considered magical:

Eye Rays. The beholder shoots three of the following magical eye rays at random

Therefore - magical petrification would be unable to affect a target within the sphere, and both the on-going saving throws & petrification condition itself would be supressed if the targets enter it while affected.

Does suppressing petrification stop the on-going petrification effect?

If the petrification is considered magical, it will be suppressed, both by Antimagic field & the Beholders own Anti-magic eye cone.

On a failed save, the creature begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a success, the effect ends.

If the effect is suppressed, the target doesn't make a saving throw, but it also states that the effect is only ended on a success. Therefore the effect continues until the target succeeds on a saving throw.

Answer 2

It suppresses/prevents only if the creature's ability is magical

Some of the abilities of these monsters are considered magical, some are not. To define if something is magical or not, the Sage Advice Compendium gives us a small questionnaire:

• Is it a magic item?
• Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description?
• Is it a spell attack?
• Is it fueled by the use of spell slots?
• Does its description say it’s magical?

If you answer yes for any of these questions, the ability is considered magical and thus suppressed by an antimagical field.

Now, between the beholder and the medusa, only the beholder's eye rays are magical. Let's take a look at the beholder's eye rays description (emphasis mine):

The beholder shoots three of the following magical eye rays at random (reroll duplicates), choosing one to three targets it can see within 120 feet of it: [...]

In addition, the description of the Antimagic Cone feature says it works against the beholder's own eye rays (see below), suppressing the petrification effect all together for a targeted creature. If the target is making saving throws against being petrified and enters an antimagical area, it stop making saving throws while it stays in that area, and continues to roll saving throws after leaving the field.

The beholder's central eye creates an area of antimagic, as in the antimagic field spell, in a 150-foot cone. At the start of each of its turns, the beholder decides which way the cone faces and whether the cone is active. The area works against the beholder's own eye rays.

The medusa's (including the undercity medusa introduced in Ravnica) petrifying gaze, however, answer every question of the "Is it magical?" questionnaire above with a no, so a creature petrified by it remains petrified under the effect of an antimagic field.

Antimagic field also suppress the petrification of both the basilisk and cockatrice abilities, respectively (emphasis mine):

Basilisk:
the basilisk can force the creature to make a DC 12 Constitution saving throw if the basilisk isn't incapacitated. On a failed save, the creature magically begins to turn to stone and is restrained.

Cockatrice:
[...] and the target must succeed on a DC 11 Constitution saving throw against being magically petrified.

Answer 3

Suppress: Yes (but not as you think), Prevent: No

A creature's ability to petrify may or may not be magical. If it isn't, antimagic can't affect it.

If it is magical, then:

1. if the target its in the antimagic field when the monster uses the effect, it will not work.

2. if the creature has been petrified (or is no longer at risk) the effect has finished and antimagic cannot affect a magical effect that happened in the past.

3. If you are in that limbo area between the creature's action and the end of your turn then the effect is suspended (i.e. you are not restrained and do not make the saving throw) until either the duration of the effect expires (AFAIK, none of them have durations so this is irrelevant) or you leave the antimagic zone at which point you become restrained and must make the saving throw at the end of your next turn.