"Using a lacrima is like borrowing magic" Ciskel started to explain as he picked up another lightning crystal. "You cast the magic like you normally would, only when you try to cast things that are beyond your range of skill or element, you normally fail. Well if you have a lacrima that can substitute that power you can do all sorts of stuff."
Ciskel pointed at a tin can as he increased its weight. It fell to the ground. "Now watch as I try and add lightning"
The tin can started to spark a little. Suddenly all nearby tin cans moved towards the tin can on the ground and slammed into it.

"See? Gravity plus electricity makes magnetic fields!"

Then he picked up the grey lacrima Drake filled. "However your magic is of a different kind. It's a negative to our positives."
He held the crystal tightly as he focused on another can.
The can simply moved up and down as Ciskel altered its weight up and down.
Ciskel however had a confused look in his eyes. "It's reversed...", he pondered this... "Cool!"
He passed on the crystal to Ris "Can you show us what the reversed side of your magic looks like?"