Deng Shiru's Seal

Origin
Deng Shiru (1739 - 1805) was a Chinese calligrapher during the Qing Dynasty. His style name was 'Wanbo' and his nickname was Gu wanzi, his main style was that in seal script. It evolved organically out of the Zhou dynasty script and Shiru often wrote ancient coded messages to the Qianlong Emperor for his eyes only. The sixth Emperor worked directly with Shiru to figure out the cypher so no one else could read their messages.

Effects
When Shiru was done with a message he would seal it with his wax seal, to help keep the secrets between the two friends the seal prevents anyone from opening the letter. With the seal applied the letter cannot be torn open, damaged or normally opened unless you are the recipient of the letter.