Ancient Elven Boots

The Ancient Elven Boots are found by asking Ser Bryant in the Lothering chantry "Is there any other assistance you can provide?". He will give you the key to the locked cabinet and you will find the boots there. There is a known bug in the PC version of the game that prevents the boots from appearing in the cabinet. The only way to get them in the PC version is to use the Dragon Age toolset, either downloading the unofficial files or modifying it yourself to add the boots in.