A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
Map of the Northern Colonies reads "Other players' Terrains will not destroy your Terrains at this Item's battlefield."
The Ivory Legal terrains all read "Destroy a Terrain (if able). Put this Terrain into play."
I'm assuming this means the other player can still play their terrain, it just also leaves yours in play? In this case, it would seem like you can play a second terrain, destroy the opponent's, and thus have two terrains in play?
Map of the Northern Colonies reads "Other players' Terrains will not destroy your Terrains at this Item's battlefield."
The Ivory Legal terrains all read "Destroy a Terrain (if able). Put this Terrain into play."
I'm assuming this means the other player can still play their terrain, it just also leaves yours in play? In this case, it would seem like you can play a second terrain, destroy the opponent's, and thus have two terrains in play?
It's a lot to go through, but if all the pieces line up as you have laid out, yes. In the example you've provided, you would be left with two Terrains in play.
Map of the Northern Colonies reads "Other players' Terrains will not destroy your Terrains at this Item's battlefield."
The Ivory Legal terrains all read "Destroy a Terrain (if able). Put this Terrain into play."
I'm assuming this means the other player can still play their terrain, it just also leaves yours in play?
Correct. There's no longer a restriction in the rules regarding Terrains, it is just in the terrain cards themselves that they can't enter play if there's already one (80% of Emperor) or that they destroy a pre-existent Terrain (Ivory)
In this case, it would seem like you can play a second terrain, destroy the opponent's, and thus have two terrains in play?
Yes, you get to choose which Terrain you want to destroy if there's more than one. Map of the Northern Colonies allows this scenario of having multiple Terrains in play.