Optical quantum memories based on Er, with its telecom-compatible optical transition, could benefit quantum networking and linear optics quantum computing applications, if the requirements for high memory efficiency, fidelity, and storage capacity can be met simultaneously. Here, we demonstrate the first high efficiency memory in Er, with spin-state storage for 25 μs and classical efficiencies up to 81%, using the rephased amplified spontaneous emission protocol. We show quantum storage along with high-fidelity entanglement of an output state and the state stored in memory, and a demonstration of multiplexing storing 70 modes in the temporal domain. We use the results to discuss how, with modifications to the pulse sequences and experimental geometry only, the performance can be improved to meet the requirements for practical quantum applications.