Alright, minor details from the next issue of CoroCoro. Y'all know where to look for the pictures. Take with a grain of salt, that last faked issue looked pretty real.
The article talks about Combination Attacks, exclusive to multi-battles (Double, Triple). Basically, do moves in a certain order, and have 'secondary effects' occur. Most of the described effects in the article sound like field conditions, from their descriptions.
For example, using the attacks Grass Oath, Fire Oath, and Water Oath:
Grass Oath, then Fire Oath -> Field of Fire, causes damage to opponents each turn. Think of a field of grass set on fire.
Grass Oath, then Water Oath -> A Moor attack, drops opponent's Speed. Think of a swampy-type environment, like a marsh.
Fire Oath, then Water Oath -> A Rainbow over the field, making secondary effects for your allies and you more common (It may be something like Serene Grace...). Think of the sun shining through a rain shower.