Arkbow

The Arkbow is a magical artifact in possession of, and attuned to, the planeswalker Vivien Reid. It contains an invocation of every creature that ever lived on Skalla, and many more added on other planes.

Origin
The Arkbow was created by the Nura and Smaragdi, after their world came under threat of Nicol Bolas. The plan was to use the Arkbow in a last stand battle against the draconic planeswalker. But as the battle was lost, Vivien instinctively planeswalked to safety with the Arkbow.

Use
In her early days as a Planeswalker, Vivien struggled to understand the Arkbow, which seemed to have a life of its own. At first, the creatures called through the bow were weakly incorporeal – ferocious but dim, ghostly versions of themselves. But as she traveled to new planes, encountered new creatures, and added them to her menagerie, the Arkbow grew in power. Soon she could call the magical spirit forms of creatures from myriad planes, beasts greater than anything that had ever lived on Skalla. Vivien can summon these spirits into battle by firing arrows at her foes.

Adding new creatures
The Arkbow can make "snapshots" of a dying creature, transforming its memory into a spirit of the animal in its prime. The ritual involves tapping the Arkbow three times against the floor, resulting in an intense white light surrounding the caster. After a fourth tap, the artifact opens into metallic bark and branch, flowering at intervals. After it splits down, the jag of light absorbs the spirit of the dying animal.

Trivia

 * The properties of the Arkbow share similarities to the practices of the Ghostslaver necromancers on Grixis. In that both enslave souls and create ghosts to act as servants. The key difference is the Arkbow can only bind the souls of animals and later create the ghost of an animal.