Mana Pools and Anima Jars are special Arcane Devices that allow the storage of mana and animus respectively. Wizards, clerics, druids, and animages all may create these devices subject to the limitations of the spells or disciplines that govern the creation of Mana Pools and Anima Jars.
In general Mana Pools are constructed from highest quality gemstones. Anima Jars are usually, but not always, finely wrought crystalline containers that may be sealed. The amount of mana or animus that may be stored depends upon the material from which the device is made, the abilities of the creator of the object and the limitations of the spell or discipline used to create the device.
In all cases, the mana or animus stored in these devices may only be accessed through the use of mana and animus links (respectively). In the case of professions such as wizards, where such fine distinctions are not made on links, a simple object link is sufficient.
Mana Pools and Anima Jars are extremely useful devices allowing mana and animus wielders to greatly extend their power. Any mana wielder may use any Mana Pool or Animus Jar made by others, as long as no current link to an owner exists. If such a link already exists, then if the individual desiring to use the Mana Pool or Anima Jar is capable, he or she may attempt to break the pre-existing link. However, the destruction (or even willful release by the owner) of a link to a Mana Pool or Anima Jar destroys the Anima Jar or Mana Pool.
One of the first things attempted by overly ambititious mana wielders when Mana Pools and Animus Jars were first discovered was to try and use multiple pools at one time. Unfortunately this tragic expermient met with great disaster and resulted in what was posthumously named Michael's First and Last Law of Animagic Containers. The law states that the animagic feedback through linked animagic pools is proportional to the square of the number of pools.
More simply speaking, using multiple Mana Pools, or multiple Anima Jars in series (or parallel) is extremely dangerous. Using one of each is no problem as Anima Jars and Mana Pools do not resonate, nor add to each other's feedback. Specifically whenever a mana wielder attempts to use multiple Mana Pools or multiple Anima Jars the chance of magical fumbling skyrockets in proportion to the number of mana pools OR anima jars linked to the weilder (note jars do not create feed back with pools, pools resonate only with pools and jars with jars). This applies to all classes, the chance of a resonance feedback scales in proportion to the number of pools or jars in the link.
Thus for safety reason's very few mana wielder's ever employ more than one mana pool at a time. The only known exception to this is the spell Mana Wheel, where somehow the creator of the spell got around this limitation. The details of this breaking of Michael's First and Last Law of Animagic Containers has puzzled more the a few hundred magical theorists. The best guess is that somehow the very mana draining nature of the spell keeps the feedback minimized.
Other linkages
One common confusion is that mages often tend to have multiple mana pools on them. However, generally only one, maybe two pools are for the wizard's own personal use. Most of the other mana pools have links to other magic items on the mage's person. While typically an Arcane Device that used a mana pool would have it's own mana pool, sometimes that item is too small to mount a gem of the correct size, so the creator may have created two matching pieces of jewelry, say a ring and pendant where the ring actual mana pool for the ring was in the pendent, or perhaps someone later reworked the ring to add an extra mana pool. There are many possiblilties.