The "Containermancer" is focused around moving containers that are filled with explosives. This tactic, when done properly, allows you to deal massive, if not fatal, damage to your chosen enemy. You can also nest containers inside containers to make an instant prison when the outer container is broken.

• Boxes/Barrels/Anything that can hold items and be destroyed by damage
  
• A character with crafting
  
• A high strength/telekinesis character
  
• The "Pack Mule" talent
  
• An unhealthy amount of grenades

By this point, you should have your army of barrels/boxes and a plethora of grenades. Now comes the time consuming part of filling your container. You'll want one grenade per slot, so split your stacks accordingly. Feel free to mix and match grenades as you please, or use multiples of the same grenades. A box with 30 Firestorm Grenades will hurt quite a bit, and a box with 5 Love Grenades, 5 Fear Grenades, 5 Tremor Grenades, etc., will be sure to alter any battle.

Once you've filled your container with grenades, quick save. It's a tiresome process, and having to repeat it is a pain.

Now that you're all saved up, pick your fight. Center of Cyseal, random boss, that evil rooster in the town square, any will do. Carefully plop down your box and prepare yourself.

Keep in mind, some NPC's will target you for dialog when they take damage, so you may have to have your box in a place where it can be useful on your first turn. A nice thing to do in this situation is to use anything nearby to corner the NPC, such as screens, tables, chairs, etc. Once combat triggers, or if you're using it where dialog doesn't apply, you're ready to start the fun.

The best way to set off the box is to either set it on fire or place it on a burning surface. You can either save a Firestorm Grenade or have a Pyromancer with Flare to create a burning patch. Once your box is on fire, stand back. Once it breaks, all of your hard work will come to fruition as the floor is covered with grenades. A few moments later, they should catch fire and cause a massive chain detonation. Whatever you were aiming at is now either dead, near death, or suffering from every negative status in the game.

If you opted for the non-lethal version, your container will be filled with other containers, one per slot as with the grenades. When you break this box open [ranged damage works best, such as a bow or Staff of Magus], the containers inside will all fall out and form a ring around the destroyed box. This should break some pathing, or at the least alter some vision cones.

Xivly - All of the grunt work in the game.
gAmmA - Making the guide look nice.
Axoren - Setting off the box.

A closer look at the images show that my characters are level 3, and i've used this technique to kill the level 7 boss outside of the Black Cove Enterance.