Leaks. How to avoid them.

Good topic, Kostya! You hit the nail on the head with these tips. I'm certainly not some super cool online hero, but to support your topic, I'll add my two cents. With one Hydra, you can take out the maximum number of Crypts by attacking the Vampires. All the other inhabitants of the Necropolis will just stand there and wait for the end of the battle. With two Hydras (1 stack) plus single units, you can take the maximum Hive. Without the single units, one Hydra is lost. I haven't tested the hero's parameters, but I remember that 3 defense is enough.