[Primordial] Item - Sliver of Prime Essence

These items didn't have a fully-realized visual design during their stats development. I initially had more spells laid out when figuring out the other items, but cut them due to feature bloat, so I basically crammed the remainder here. As a side effect, these slivers are now mentioned as an object needed to combine the Four Primordial Weapons.

The slivers were originally wands; eventually I picked a more open-ended look (with distinct colors and silhouette) and incorporated some of them into the Four Weapons.

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This crystalline shard is a sliver of pure condensed elemental energy, captured from the elemental planes or bestowed by a master of the elements. With right hands and composition, its power can be used to save lives, destroy cities, or forge something greater.

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Sliver of Prime Essence
Wondrous item, varies (requires attunement by a spellcaster)

This crystal can be individually used as a spellcasting focus. It can also be attached to a weapon or shield over the course of the attunement period to transform the object into a spellcasting focus.

Planar Resonance. A sliver is aligned with typically one elemental plane (air, earth, fire, or water), which determines the magic it possesses. Over the course of a long rest, a sliver can be merged with another that has a different elemental alignment, combining them into a single Primordial Sliver that has the properties of both alignments.  The number of alignments a sliver has determines its properties and rarity: uncommon (1 alignment), rare (2 alignments), very rare (3 alignments), or legendary (4 alignments). For each alignment beyond the first, the sliver grants you a +1 bonus to your spell save DC (to a maximum of +3).

Elemental Surge. When you cast a spell of 1st-level or higher using this sliver and deal damage with a spell attack roll, you can deal an extra 1d6 magical damage of a type based on the sliver's alignment: bludgeoning (earth), cold (water), fire (fire), thunder (air). If the sliver has multiple alignments, you choose one alignment and its associated damage type.

Elemental Spellcasting. The sliver has charges based on its number of alignments: 2 charges (1 alignment), 4 charges (2 alignments), 7 charges (3 alignments), or 10 charges (4 alignments). The sliver regains expended charges daily at dawn.  While you hold this sliver, you can use an action to expend the necessary charges to cast one of the following spells determined by the sliver's alignment. These spells use your spellcasting DC and don't require a material component.  

• Air: call lightning (3 charges), gust of wind (2 charges), seeming (5 charges), thunderwave (1 charge). 
• Earth: entangle (1 charges; appears as twisting earth), meld into stone (3 charges), spike growth (2 charges), wall of stone (5 charges). 
• Fire: blur (2 charges), burning hands (1 charge), fireball (3 charges), flamestrike (5 charges). 
• Water: cone of cold (5 charges), create or destroy water (1 charge), mirror image (2 charges), control water (3 charges).