Kandarin Diary. Principal reward: Kandarin Headgear 4 - Although it offers the same features as Mithril Med Helm, it has a number of bonus options similar to RS gold the other Elite Diary rewards. The bonuses are:
33% more efficient spinning on Seers Village Spinning Wheel, which could be useful for people who wish to make more gold coins. 15 points more of grace from Seers' Village Agility Course that can be used to make the process of farming for Graceful Outfit a bit less difficult. A possibility to transfer Camelot teleport from The castle direct towards bank's entry point. 10% more rewards from Barbarian Assault, and many other advantages.
If they can complete each Achievement for each of the difficulties in the Achievement Diary players get access to the exclusive Achievement Diary Cape, which they can buy at Twiggy O'Korn in Draynor Village for 99,000 coins. Additionally they will also be rewarded with a hood unique to the cape.
Duel Arena (Safe). Like the name implies, Duel Arena allows players compete against one against each. There are also special rules that can be set to spice things up (like taking gold coins). The site is open to both members and free to play for adventurers.
Clan Wars (Safe). The game allows two rival chats to engage in a battle against one another. There are no rewards to this sport... maybe besides glory.
The Last Man Standing (Either Safe or dangerous based on the mode). The Castle Wars area players can converse with NPC Lisa which can sign them up for LMS. It's essentially an online battleground game that is implemented in RuneScape. Rules are pretty much the same as other battleground games - players are transported to the island where they look for a item and fight each other. Game ends when one remaining player remains on the island. There's a reward of 1.5mil to the player who is first and 500k for second in competitive mode.
Castle Wars (Safe). Similar to Clan Wars it is a group contest. Castle Wars is simply a Capture The Flag mode implemented as a minigame within RuneScape. Two teams attempt to get to the the base of their opponent and remove an unprotected flag, which is then defended by the other players. As a reward winning team earns buy OSRS GP tickets to buy various cosmetics.
