Klephtis was the senior Guild Master in Apollonia - until he was assassinated one night. His custom made set of thieves tools were never found afterwards. One of his apprentices claimed to have been allowed to use them once and described them as "being made of divers material, keys of gold and crystal, saws of purest adamant and pliers made of quicksilverthat could reach into the smallest lock and around corners". But all know what sort of braggarts and liars thieves are when in their cups.
In game terms possessing the tools gives a thief +20% to Find Traps, but oddly no bonus to remove or disable them. And a +15% bonus to Open Locks.