Watch Commander and, more recently spoiled, Voice of the Ancestors as examples.
Does this work like Restricted, so a character can attach a second copy and discard one of them?
Or does it prevent a second copy from attaching?

Just now, Bayushi Shunsuke said:

Watch Commander and, more recently spoiled, Voice of the Ancestors as examples.
Does this work like Restricted, so a character can attach a second copy and discard one of them?
Or does it prevent a second copy from attaching?

These operate almost like the restricted keyword: After you play a Spirit attachment on a character, if any of them have “Limit 1 Spirit per character,” you must discard all other Spirit s on that character (other than the one just played).

[Tyler Parrott, June 20 2019]

“Limit 1 Battlefield per province” means there can only be 1 Battlefield attached to that province, regardless of player.
If a player plays a Battlefield attachment on a province, it will discard all other Battlefields attached to the same province.

[Tyler Parrott, Mar 2 2020]