Ava's accumulator is a reward from Animal Magnetism if you have 50 Ranged or higher upon completion (players with lower than 50 Ranged will instead receive Ava's attractor). Ava (found in Draynor Manor) will upgrade the attractor for anyone who obtains 50 Ranged after the quest, for a price of 75 steel arrows. After that it can be upgraded to Ava's assembler, for 75 mithril arrows and vorkath's head or 4999 coins. Upon dying, if it is not an item kept on death, it must be re-obtained from Ava for either an Ava's Attractor or 999 coins, in addition to 75 steel arrows. Multiple devices may be bought.
The accumulator gives the second best Ranged attack bonus for the cape slot.
The accumulator, like the attractor, can pick up a player's ammunition after they fire it. The accumulator also randomly attracts metal items (steel arrows, darts and knives, iron ore, toy mice, steel med helms and iron nails) into the player's inventory. If the player's inventory is full, the attracted item will be dropped at their feet. The device will not pick up objects while you are wearing a metal platebody or chainbody with a negative Ranged attack bonus, as the metal armour interferes with the magnetic function of the accumulator. However, metal armour without a negative ranged attack bonus (such as Carnillean armour), as well as platelegs, helms, boots, shields, and weapons, will not interfere with Ava's accumulator. Note that Ahrim's robetop will interfere with Ava's accumulator, despite it being mage armour.
As of 20 February 2014, players can toggle the collection of random metal items by right-clicking the accumulator and selecting "Commune".
Ammo recovery rate
The breakdown of the ammo recovery rate is as listed:
Break on impact: 20%
Drop onto floor: 8%
Recovered automatically: 72%