Here's an Idea...

##What if all crystals and gemstones were able store power, energy and magic in the same way that you can store electricity in a battery. Gems, crystals, abyssal pearls, moonstones, true ice and nexus follow the same principles that make up the Brackern.

Note: This is mostly based on old lore and is basically headcanon at this point but I feel like could work in the current lore.

The Brackern are beings that through ritual were able to bind their life essence to crystals. Able to store their very being and power to an object. If all cyrstals were naturally capable of this perhaps it would explain why the the brackern were so easily corrupted by the ambient magic produced by the War. It would also explain the origin and nature of quite a few objects in Runeterra and the actions of certain champs:

• True Ice might simply be crystals attuned to the magic of the watchers and the frigid cold of the north. Explaining why it seeming never melts. Ashe's ult being its namesake.

• The Abyssal Pearl gathered the dark energies found at the bottom of the Great Deep. To what end the landwalkers might use such an item is unknown but it would be powerful of its own accord.

• The Moonstone in exchange is a warding stone that stores the power of the moon itself.

• Taric appears to know the nature of gems and crystals. If his VO lines remain true, then he understands that certain gems have certain functions and grant different benefits and power.

  • Emerald for insight.
  • Opal for harmony.
  • Ruby for vigor.
  • Sapphire for divinity.

• The Nexi are now more game mechanic than they are lore. But even if Summoner's Rift doesn't exist, it does seem to be a reflection of sorts of the world of Runeterra. A Nexus may simply be a crystal storing the more ambient magic and energy of the world. The larger the crystals the more power it can store. Crystals of this type would undoubtedly be fought over if the magic were more raw in nature and easily manipulated to suit your needs. Xerath was and may still be seeking nexus crystals for this very reason.

• With the Bard video we are introduced to a new magical "egg" that appears to be very gem-like to me. Perhaps this "Egg" stores the essence of the another being. Ao Shin seems to be a good candidate as others have suggested. Or perhaps it simply stores the energy of the cosmos itself. That seems like magic worth the time of Bard to interfere for.

EDIT:

• Kassadin's passive, Void Stone, seems to imply that he has a crystal that absorbs magic.

• The in game item, Zz' Rot Portal, seems to be made from void crystals as well; allowing voidspawn passage onto the Rift.