Battle Points are special points you gain while battling. You can only gain points from battling players, and only if those human players have a battle rank close to yours.
Every time you fight a battle and win, you may earn Battle points. The amount that you earn depends on what your Battle Rank is, and the Battle Rank of your opponent. However, If you lose the battle, you will lose some battle points.
The table below shows how many Battle Points you will earn or lose from a battle, with X being the number of your battle rank.
Enemy battle rank
Battle Points earned
Battle Points lost
X - 7 and lower
X - 6
X - 5
X - 4
X - 3
X - 2
X - 1
X + 1
X + 2
X + 3
X + 4
X + 5
X + 6
X + 7
IMPORTANT! You Will lose Rank if you lose enough battle points and fall to the lower rank. For example, If you are High King and you drop below the required minimum battle points to become High King, you will drop to a rank to King. This has been proven many times. Make sure you maintain your rank by keeping an eye on your battle points.
There are currently 21 different battle ranks, and the 21 ranks are divided into 7 different tiers. The final tier, containing rank 22, is as of yet not completely confirmed but Castle Age does contain an image/icon for this rank.
As a player reaches certain amounts of battle points, they will be awarded an increased rank, a new title and a reward.
Once a battle point amount is hit, a player will maintain the best TIER (NOT Rank) achieved, even if their battle points fall below the threshold. A player Will fall down a Rank if they lose enough battle points. Keep an eye on your battle points so you maintain your rank.
Unfortunately, if battle points fall below what's needed for a rank, any item, magic, or soldier rewards won't be purchasable ("(locked)" will appear instead of amount drop down menu) in Town until needed battle points are regained.
Players that have not engaged in Battle will have a rank of zero with the title "No Rank".
At present (Jan 2011), the game will not allow a player to accumulate more than 100,011 battle points, or 100,000 plus any remnant from the previous battle won. A player can lose battle points and re-accumulate them to reach 100,000 again, but there is no 'pad room' above the 100,000 level.
For gaining battle ranks, you can earn a variety of rewards. In each tier, there are 3 separate ranks. For the first two ranks in a tier, you will earn 5 skill points for reaching that rank. For the third rank in each tier, you gain the ability to buy special units, armor, or magic. Each item has an incremental cost. This means that every time you buy these items, the cost to buy them will increase (just like buying land). Below where it says "incremental cost", it means that for every 1 that you buy, the price will increase by the incremental cost. If you buy 5 at a time, the next time you buy that item, the cost will be the original cost, plus the incremental cost times 5. So if the base cost is 350,000, and the incremental cost is 35,000, after buying 5 items, the new cost is:
350,000 + (35,000*5) = 525,000
Rank: Elite Soldier
Reward: Ability to buy the Gladiator Sword (Weapon)
Cost to buy 500: 129,750,000,000 (one at a time) or 128,750,000,000 (5 at a time) or 127,500,000,000 (10 at a time)
Important Note about Buyables
You should try to maintain enough battle points to qualify for your current battle rank or you WILL fall to the rank below. If you are a high general, and your battle points fall below 32,500, you will not be able to buy archangels. However, once you get your battle points back up to 32,500, you will again be able to buy archangels. Thankfully, you will only run into this problem with the units/weapons/magic items you can buy. You will never lose the bonus skill points you earn from battle ranks.
Champion's Auras, Royal Seals and Arcane Blasts (War) are the only type of magic you can buy. This makes them very valuable, since normally you can only get magic through quests, monster battles, gifts, Oracle purchases, or gambling on Treasure Chests. Neither one of these Battle Rank magics have an upkeep, and are generally better than the magic items available as gifts and most quests.