assume the mantle
To take, inherit, or receive the responsibilities and duties associated with a certain position or job, especially one regarded as important or powerful. The king led the country for over 60 years; now, his daughter will assume the mantle of the throne.
assume the position
1. To take over the role and responsibilities of a particular job. My boss wants me to assume the position of treasurer this year, but I don't know if I want the extra workload.
2. A command issued by US law enforcement officers, meaning to stand with one's back to the officer and hold one's arms in a position to be either handcuffed or frisked. Primarily heard in US, South Africa. I knew I was in trouble when they asked me out of the car, but I knew I was going to jail when they told me to assume the position.
assume liability for
To take responsible for something, typically a cost or expense. When you signed the contract, you assumed liability for fees like this.