Diamonds are mainly purchased with real-world money, and serve to improve many parts of the game's experience. Also, by spending large amounts of them you are eligible for certain special prizes. This is sometimes contemptuously referred to as "pay to win", but it's also the main revenue generator for the game creators.
Diamonds can be won in-game, although only in small quantities. The only guaranteed way to get them is as prizes (non-repeatable) you get when you reach a new Kingdom Level.
The standard price in shop, without promotions, is $2 for 20 diamonds, while the best regular offer is $200 for 2600 diamonds. Thus diamonds range from $0,08 to $0,1, or 10 to 13 diamonds to $. While this looks cheap, you should be aware that standard consumables range from 20 to 100 diamonds ($1,54 to $10), while items and upgrades costing up to $20 are not uncommon. Even worse, there are some purchases that are made in diamonds and have no confirmation screen, thus you can quickly deplete your reserve unless you employ great care. In Grotto Bank, you will get diamonds depend on your money.
There are also some events and promotions offering better rates than this (up to 25 diamonds/$) but they are not always available. Some are one-time only, some are time-limited (linked to events or you can only buy them at the beginning of your kingdom), and some have a limit of how many can you buy.
- Main upgrades
- Unlock more patches of land at the Manor
- Unlock the third Supply Station slot (Armor Games)
- Upgrade a Training Grounds Slot to more than 20% bonus Hero Experience
- To buy shards to upgrade hero rank (almost inevitable for Durin Atomika)
- Secondary upgrades
- Unlock more Training Grounds slots (not efficient, it's better to upgrade a single one)
- Unlock more positions on the Inventory (not really needed)
- To pick more cards in the Tavern (too expensive for a little improvement)
- To buy hearts for heroes (not recommended, can be bought for Honor Stars)
- To buy Heroic Medals to augment heroes. (not much recommended, they can be won for free)
- To buy resources to upgrade Towers and Magic Skills. Suboptimal, since mere time and energy will give you Level Taxes to upgrade anything.
These are ways to improve your gaming experience. They can all be substituted with resources won from the game itself, although never as easily or conveniently .
Almost all cooldowns in the game can be shortened or eliminated altogether with diamonds, but reducing cooldowns is simply not efficient unless you're buying diamonds by the thousands.
- Temporary boosts
- Improve training quality on the Training Grounds
- To have more attempts at Monster's Den, either on Boss Clash or Blitz Acres
- Additional Kingdom Tax collections
- Use Crown Port and Mysterious Island remaining attempts
- Substitute gold in Manor, Supply Station and Training Grounds
- Buy time of Fairy Blessing and Fairy Alliance
- Battle Drums in Blitz Acres: Increase your soldiers and tower damage by 10% (costs increase by 20 each time you buy)
- Morale boost in the Cyclops King and Poseidon Boss Battle: +20% damage, no chance of failing
- Late sign-in in the Daily Check, 2 diamonds
- Buy event items
- Performance improvements
- To fully Disassemble equipment, recovering all costs
- Gold Hammer in the Forge: No chance of failing when armoring equipment. (Can be substituted by normal armoring, and just tough it if you lose a shard: there will be more)
Consumables bought for Battles
- Big Cache: 200 goods for 15 Diamonds. It's just not cost-effective.
- Longevity Card: 5 lives for 20 Diamonds. Expensive but useful (especially on Heroic and Hard Scenarios)
- Cold Wand: Freezes enemies for a short time for 15 Diamonds. Expensive, and of relative utility unless you're losing the battle by a really tiny margin.
- Potent Bomb: Kills all non-boss enemies in the map for 50 Diamonds. Potentially life-saving, though very expensive.
Spells, consumable one-time effects that affect battles.
- Blitz Acres:
- Wrath of God: Costs 30 diamonds, kills all enemies in the screen, gives back lives, improves 30% damage of your towers for 3 waves.
- Common battles: You will see an overlaid screen, when you run out of lives, offering you three choices. IMPORTANT NOTE: There is no confirmation screen for "buying" these: if you have the requisite diamonds, they will be spent with a simple click. Thus, if you see the battle is clearly lost, you should better quit before being overrun. If you accidentally spend the diamonds, contact support with a request for a refund.
- Rains of Life: Costs 15 diamonds, give back 3 life. Since you will usually see this after being overrun, it's not very useful. At most it could let you get more stars if a single creature got past your defenses. Plus, a Longevity Card gives you 5 lives for 20 diamonds.
- Ice Age: Costs 25 diamonds, same effect as a Cold Wand, plus it gives 3 lives. It may make sense costwise, since the Cold Wand alone costs 15 diamonds, but same as Rains of Life, odds are that by the moment you get to buy this, you simply lost the scenario and will do better to restart.
- Razing Blast: Costs 50 diamonds. Same effect and price as a Potent Bomb, plus it gives 3 lives. This is the only option that makes sense, both in cost and as an effective tactic, but only in Heroic and Hard scenarios. On Easy scenarios with 20 starting lives, using this will probably result in less than three stars (you already lost all your lives), thus forcing you to do it again in the future. Unless you spend even more diamonds in Longevity Cards.