So, what is the Don the Disguise quest? Well, for this quest players have to don the disguise and then go on to shatter three resonant crystals at the Spire.
Fortnite's Don the Disguise and What to Do Next
As the last of the quests for the Spire Challenge, you should have already gathered all the items Raz needs to make the disguise. The disguise itself can be found at the foot of the Spire, through the village (right in the lower levels), and to the end of the path. It will be beside a wooden fence.
Don't worry though, it glows blue/purple so you can't miss it!
Once you have donned the disguise, you will need to make your way back up to the tower. But how do you find the crystals? Easy enough, along the left wall there should be pink crystals. Using a pick, hit them and you're done!