The Corruption Meter is a meter that goes around a beating heart in the middle, near the Battery core. The meter's capacity can be increased through biting pedestrians, staking Vampires, and collecting Canopic Jars. Canopic jars, when shattered, increases the capacity of the Corruption Meter, similar to how Blast Shards increase Battery Cores. New powers like Shadow Swarm and Shadow Stake can be activated as long as the meter is not empty.
Shadow Swarm can be used for the duration of the meter's capacity, so it's probably best if the meter is full in order to use the power more effectively. Shadow Stake can be used as many times as the meter allows it to be.
Blood stored in the Corruption Meter depletes slowly over time so filling it up frequently is necessary if one is to use Shadow Swarm. Also when the Corruption Meter is empty, the beating heart in the middle starts to beat rapidly although this has no effect in-game and once it has been filled up again the heart will go back to its normal beating rhythm.