At it's core,
Skylanders: Swap Force is the same game. You play through an adventure that pits your small army of figures against the forces of Kaos as he implements a new plot. Along the way, you will level up your characters (the new level cap is 20), buy upgrades and wear a plethora of silly hats as stat-boosts.
Last year, Giants added eight larger characters to the mix, as well as new characters and the Lightcore series. This time, the major new mechanic comes in the way of Swap Force characters. These 16 figures come apart at the waist and snap together via their magnets with other Swap Force characters. The result is a mix of elements and abilities that makes each swapped-pair more flexible than it was in its original form. The console versions of Skylanders: Swap Force come with the fire-type Blast Zone and the water-type Wash Buckler. Swapping their pieces gives you two new characters, each one a water/fire combination. One of the places this really comes in handy is the new element gates that require two different types of elements to get through. But wait, there's more. Both the top and bottom parts have their own ability tree. This is combined with new side-quests called Swap Zones. These are areas that only certain types of feet can access. Some are races in the air, some are a series of trampoline jumps, some are wall climbing, while others are pinball-style bouncing.
The end result is that Swap Force has a lot more gameplay for those that have the compulsive need to complete everything. After all, the game still has the single-element gates, extra objectives and lock puzzles (actually those have changed) as before. While you can run through the game's story and stop Kaos' current plan, doing so won't even get you to the 50% mark, so expect to be replaying the levels several times in order to get all the goodies and truly finish this game off. Of course, that's not really possible until all of the new figures come out.
So what is Kaos up to this time? Well, there is a volcano that erupts every 100 years. When it does, the magic of Skylands gets rejuvenated, but only if the four Elementals can get there and imbue the volcano with their magic. Kaos plans on using petrified evil to turn at least one of the Elementals evil. If he can do that, then the resulting magical explosion will turn all of Skylands evil. Of course, the Skylanders can't let that happen, so they journey with Flynn to Woodburrow, the town closest to the volcano, in order to make sure everything goes smoothly.
Outside of the game's lengthy single-player story, there are also Arena Challenges and Bonus levels. These can be unlocked by progressing through the story and earning stars as well as completing Swap Zone Challenges in the levels. The arena games include everything from Single-Player Survival to Co-Op and Vs. Survival modes. Ring Out and Arena Battle also return letting you and a friend try out some one-on-one fights without the distractions of the other modes.