Lifeblood = most essential

لازم و حیاتی/ عامل حیاتی

He is the essence, the lifeblood, the very marrow of the team

the movement of coal was the lifeblood of British railways

What gives the series lifeblood is excellent writing, inspired acting and good characters

چیزی که به سریال جان و روح می دهد، نویسندگی عالی، بازیگری الهام گرفته و شخصیت های خوب است