For defence your castle find the best strategy.
Just protect your castle.
Each wave you will fight against stronger enemies
You can buy archers all time. Archers most important feature is unlimited purchaseable and they are effective against single targets.
Wizards are able to buy after 10th wave. You can buy just two wizards. Wizards most important feature is heavy area damage.
You can unlock your special power at 25th wave.It's using increase damage for a certain period of time.
You can upgrade your archers, wizards, special power and castle health.