A proposed defence against Legilimency, I have heard this one called a variety of things. The basic idea is to visualise something familiar and “hide” or “store” your memories “within” this location or structure. “Sorting” or “organising” your memories this way supposedly makes it harder for an attacker to find them.
The basic idea seems to be related to Method of loci
Personally I do not fully get this one as a defence. The idea seems to be that the attacker will be fooled by the visualisation technique, and will see the mnemonic instead of the real memories. I suspect it would come down to a mental strength contest. Can you hold your visualisation in place instead of actually remembering things as the attacker hunts for memories?