[...] In addition to serving as mundane manacles, the shackles prevent a creature bound by them from using any method of extradimensional movement, including teleportation or travel to a different plane of existence. They don't prevent the creature from passing through an interdimensional portal.
You and any creature you designate when you use the shackles can use an action to remove them. Once every 30 days, the bound creature can make a DC 30 Strength (Athletics) check. On a success, the creature breaks free and destroys the shackles.
The antimagic field spell:
[...] The properties and powers of magic items are suppressed in the sphere. For example, a longsword, +1 in the sphere functions as a nonmagical longsword [...]
First: are the locking mechanisms on the dimensional shackles magical, are they not magical, or do they not exist and the shackles are held together by magic? Depending on the answer to the former question, what are the implications to the following questions:
- Do Dimensional Shackles simply become mundane manacles in the field?
- Will Dimensional Shackles remain on the bound creature at all; Are they held together by magical means and fall off in an antimagic field?
- Will they still have a DC 30 strength check to break, or will the be broken by a 20 which is what is needed to break mundane manacles?
- Can the selected creatures still simply remove them with an action?
- Unlike manacles, there is no DC for using thieves' tools; does this change when entering an antimagic field? (in fact, in pictures I have seen, Dimensional Shackles don't seem to have a lock or anything holding them together for that matter)
Not having a DC for thieve's tools is my premise for whether the locking mechanism is magical in the first place. This can go both ways though, it could be that magic keeps tools from picking the lock.