Ardougne cloak 4 is a reward for completing all of the Ardougne Tasks, including the elite tasks. If lost, it can be reclaimed for free from Aleck in Yanille. It has numerous useful functions, such as providing teleportations to the player and stat bonuses.
From Ardougne cloaks 1, 2 and 3 Edit
Reduced chance of being caught when picking pockets or stealing from stalls anywhere in RuneScape
Adds a chance of creating more runes in the Ourania Runecrafting Altar (rune output is increased by roughly 15%, and no extra experience is gained from the extra runes)
Magical traps on chests will teleport the player to Ardougne's North Bank, instead of a random location
Most of the drops in the Creature Creation activity in the Tower of Life will become noted
10 seconds of immunity after teleporting to the Wilderness with the Wilderness lever in Ardougne (not the Edgeville one that leads to the same location)
A player restoring summoning points with the cloak.
Teleport to the monastery south of Ardougne, with unlimited charges
Teleport to the allotment farming patch north of Ardougne, once a day
At all times
Ardougne cloak 4 only Edit
Teleport to the allotment farming patch north of Ardougne, with unlimited charges (up from once per day)
Restore all Summoning points, once per day
At all times