The Wall of Failed Tales is dedicated to listing every failed tale. Later on, EAS began adding Characters that had died to the wall. According to the first book, there are hundred (maybe even thousands) of Failed Tales on the wall that only happened in the last century (Chase later says that the Failed Tales on the wall happened in the last 200 or 300 years, not 100 years). In Rory's head, she is mulling over how half of the Tales that Characters get are failed. Chase then says that the death rate has changed since the Director placed new rules on bringing companions on Questing Tales. He thinks, at least.
In the first book, of Giants and Ice, Chase and Adelaide scare Rory by showing her the Wall of Failed Tales. Rory is afraid she will end up on the list of failed tales. Later on, Rory is afraid that Lena's name will have to be engraved into the wall because she is afraid that she, Chase, and Rory will fail Lena's tale (Jack and the Beanstalk).
In the last book, after Hansel dies, they describe how the people who were there when he died get to carve a letter in his name.