There are 15 wellsprings, 8 of them known and revealed to the Valkyrie
There are 15 small chambers around each wellspring. When a wellspring is first discovered, 14 chambers are empty, and one chamber contains an amulet. From visions recieved by Valkyrie, the chambers represent the 15 wellsprings on Valhalla, and that one amulet is found in each wellspring upon its discovery. Possession of these amulets is critical. If Utgar was allowed to obtain the amulets the results would be catastrophic.
Around each wellspring are several slightly-raised panels with ancient runes. The rune inscribed on two side-by-side panels shows a circle of swirling rocks with a star at its center. When a Valkyrie places one hand on each of these panels and concentrates, his/her visions becomes more realistic, more vivid and intense. The key is to continue pressing these panels and concentrating, for this will open a portal through which powerful heroes and armies from other worlds and eras may enter.
As the portal opens, a spiral of crystals and rocks rises up from the wellspring. A bright blue light pours through the center of the portal. Then, the Valkyrie quickly flies into this light and through the portal, then uses his telekinetic powers to bring the hero or army through the opening.
Jandar's Vision of Utgar
My recent visions show Utgar placing one of the 15 amulets in each chamber of a wellspring. He forces a captive human to press his hands against the two panels. A portal opens to the planet Earth, and the next event is so horrific that it sends shivers of fear throughout my entire being: a horde of Marro and their minions fly through the portal, Earthbound and feverish to invade and conquer. We must not, we will not, allow these events to occur.
I believe that the Valkyrie who possesses the 15 amulets will gain the ability to control his visions, and will thus be able to invade other planets via the portals. Likewise, a Valkyrie who possesses all of the amulets will be able to return all heroes and armies to their home planets. You must relay this information only to Valkyrie who swear their allegiance in this war against Utgar. These are my orders.
The origin of the wellsprings is unclear. They seemed to be partly a natural phenomenon of Valhalla, however each wellspring also seems have contruction built around it, various runes, pillars and chambers are found at each wellspring site. Each wellspring has exactly 15 chambers, 14 which are empty and one which contains an amulet. The builders of this sites are unknown, but are presumed to be ancient kyire in a byegone era now lost to history.
The wellsprings seem to be a sort of window which show warriors and soldiers locked in great battles and epic wars. What the wellsprings show seem to be random, each General appears to have only a little control over what they see. When a General sees beings who share their ideals, be it justice, power, honor, or evil, they then attempt to summon them, passing over beings that do not.
Wellsprings feed the World tree Yggdrasil.
Heimdall may have sacrificed one of his ears in return for his heightened power of hearing (according to Gylfaginning he can hear grass growing on the earth or wool on the backs of sheep), depositing it in the well in much the same manner that Odin pledged an eye to the Well of Mimir in return for knowledge and wisdom.
Regarding Mimir's Well: Mímir's Well (Old Norse Mímisbrunnr) is one of three wells at the roots of the world tree Yggdrasil in Norse mythology. The well is named after Mímir, the figure charged with guarding it and is fed by a fountain inside it called the fountain of Mímir, which granted wisdom and the power to see the future.
Three Norns (Urðr, Verðandi, and Skuld) "come from" the well, here described as a "lake", and that this trio of Norns then "set down laws, they chose lives, for the sons of men the fates of men.
Urðr "rose from the well.
Norns that dwell by Urðarbrunnr take water from the well and mud that lies around it, and pour it over the Yggdrasil so that its branches do not decay or rot.