Echo
Proc
Chance to cast again at 50% damage.
Rolls between 5% and 25%, scaling with the gear score of the item carrying it.
Forge mods that grant it
Spending one of these puts the perk on your gear instead of waiting for a roll.
Rolls on
WandLanternStaff
A drop or a craft of these types can roll this perk into one of its slots.