The thing I miss, oddly enough, is astral diamonds. They are a unique D&D thing, and I really love the idea that the most valuable of gems are mined on another plane of existence. Plus, there's room for them in the gemstone tables in the DMG -- diamonds, emeralds, rubies, etc. are 5,000 gp, so they could add another gem "tier" that was just astral diamonds for 10,000 gp.
I actually wrote them up as a magic item but I have yet to use them in a campaign:
Astral Diamond
Wondrous item, rare
These small, clear gems come in every color of the rainbow, shedding dim light in a 5-foot radius. When you touch an astral diamond, you sense a faint emotion such as love, hate, joy, sorrow, hope, fear, calm, or disgust. According to the most widely-accepted theory, astral diamonds form naturally when raw emotions on the astral plane are compressed into solid form over the course of eons.
The primary use of these gems is interplanar commerce. An astral diamond is always worth 10,000 gp, and can be bought and sold at full price (not sold at half price like most magic items). They are often traded as commodities in planar marketplaces such as Sigil or the City of Brass.
I actually wrote them up as a magic item but I have yet to use them in a campaign:
Astral Diamond
Wondrous item, rare
These small, clear gems come in every color of the rainbow, shedding dim light in a 5-foot radius. When you touch an astral diamond, you sense a faint emotion such as love, hate, joy, sorrow, hope, fear, calm, or disgust. According to the most widely-accepted theory, astral diamonds form naturally when raw emotions on the astral plane are compressed into solid form over the course of eons.
The primary use of these gems is interplanar commerce. An astral diamond is always worth 10,000 gp, and can be bought and sold at full price (not sold at half price like most magic items). They are often traded as commodities in planar marketplaces such as Sigil or the City of Brass.