Is it possible to bring an Astral Dreadnaught to the Material Plane?

Question

Exactly what it says on the tin; is there any possible way to permanently bring an Astral Dreadnought to the Material Plane, willingly or not?

Answer 1

Yes

The Astral Dreadnought can't leave the Astral Plane, because of its Astral Entity feature:

Astral Entity. The astral dread nought can't leave the Astral Plane, nor can it be banished or otherwise transported out of the Astral Plane.

However, this does not prevent an Astral Dreadnought from being somewhere else, just from getting there in the first place.

Several spells can negate the Astral Dreadnought's Astral Entity ability, for example: True Polymorph. True Polymorph can turn the dreadnought into something else and states, in part:

The target's game statistics, including mental ability scores, are replaced by the statistics of the new form.

So by polymorphing the Astral Dreadnought into something else or otherwise temporarily replacing its statistics, we can remove it from the Astral plane and then return it to its normal form or otherwise restore its use of its statistics.

Answer 2

No. It cannot leave the Astral Plane at all.

The Astral Dreadnought has an ability called Astral Entity:

The astral dreadnought can’t leave the Astral Plane, nor can it be banished or otherwise transported out of the Astral Plane.

So for a feature to override this, the specific-beats-general rule (see below) tells us that it must explicitly call out this rule and create an exception to it. No such feature exists.

Please Stop Being Evil points out a possible way of circumventing this in their answer here, though I don't think it unreasonable for a DM to rule that polymorph and transporting the dreadnought falls under "otherwise transported".

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Specific Beats General:

This compendium contains rules that govern how the game plays. That said, many racial traits, class features, spells, magic items, monster abilities, and other game elements break the general rules in some way, creating an exception to how the rest of the game works. Remember this: If a specific rule contradicts a general rule, the specific rule wins.