Opening the gates.

I always considered demons to be a weak race due to their abilities, but then I decided to calculate what percentage of the initial squad a leveled-up demon could summon. So, let's start. Opening the gate at level 4 skill, along with the Amulet of Mastery, gives 45%, a couple of Inferno cities, each of which increases the number of summoned creatures by 10% - 20%, a level 40 hero with the Gatekeeper specialization - 40%, the Urgash's Will set - 25%, a skill from the Leadership branch, Master of Gates - 20%. Wide Gate Opening - we multiply everything by 2. The result is (45+20+40+25+20)*2=300.