Here is some informations about Obsidian Defenders Map for Minecraft Frostburn that you can need before download it.
How to play/Rules Obsidian Defenders Map:
Separate into two evens teams in the spawning area and take minecarts to the holding area. Once you have arrived, sleep in the beds to assure you will respawn in the correct holding area and flip the switch to indicate your team is ready. After both teams have hit the ready switch the doors will open into the arena.
The main objective is to defend your Obsidian temple while attempting to destroy the opponents. To do so a pickaxe will spawn 3m after you begin and every 3 minutes after that in the temple in the centre jungle. Acquiring a pickaxe is key to your victory.
Make your way to the enemy Obsidian Temple and destroy 2 blocks of obsidian, walk through and activate the pressure plate inside. This will will indicate victory for your team and safety for your obsidian temple.
There are several side objectives to aid you in your assault.
This includes 2 capture points hidden among the jungle. To capture a point stand on the pressure plate corresponding to your teams colour, the three redstone lamps will begin to light up one by one until the point is captured and the indicator for your team is lit up. Be careful though, capturing of a point can be interrupted by someone standing on the opposite capture point!
The advantage of holding capture points is you will gain 2 types of currency. Every minute your team will receive 1 gold ingot, which is used for purchasing items and potions from the vendors. Every 1 minute and 30s you will gain a different currency to open the sewers for you team or mend the broken bridge. The more control points you have, the better the income is!
Once the sewers are unlocked you will have access to a merchant who sells XP potions and a powerful bow.