The Ardougne cloak 3 is a reward from completing the easy, medium, and Hard Ardougne achievements. It currently offers a modest prayer bonus along with strength bonuses for all three combat styles, being behind others which are considerably more difficult to obtain (per skill or quest requirements). It is obtained from Aleck in Aleck's Hunter Emporium in Yanille, and can be reclaimed from there for free when lost. The design on the back seems to look like a highwayman's mask. This may be because Ardougne is a popular city for those who wish to train Thieving. Upon death, the cloak is automatically kept, except in the wilderness or in other areas that affect items kept on death.
Increased chance of success when pickpocketing in Ardougne
A chance of additional runes at the Ourania Runecrafting Altar (approximately 15% more; no extra experience is gained)
10 seconds of immunity when teleporting to the Wilderness via the lever in East Ardougne (but not the Edgeville lever to the same location) (bugged and doesn't work)