It can be used to project blasts of electricity and channel lightning bolts from the sky.
"Obey the command! Thunder Emperor, Come Forth!"
In the English-dub of Cardcaptor Sakura, the summoning spell is shortened to Syaoran announcing, "Element: Lightening!" or "Element: Thunder!"
Due to the difference in words and pacing of the original Japanese, the phrase would some times be changed to "Element: Lighting! Descend!" to fill the left over mouth lip-flaps in the animation.
Tsubasa Resivour Chronicles
Unlike his counterpart, Tsubasa Li doesn't use the paper charm, he simply summons the spell with two fingertips.