Meteorites are classified into 3 categories: Regular, Flares and Astral Shards. You can acquire Normal meteorites by doing stages, tower of tribulation or by doing guild towers, Flares from combining meteorites and Astral Shards by doing Daily Dungeons.
Regular meteorites raise the character's stats when equipped. You can only have of each meteorite type equipped at any one time.
Flares will increase the effect of the equipped meteorites.
Astral Shards are used when evolving a meteorite to a higher grade.
Just like items and equipment, meteorites come in 5 grades: Poor, Normal, Rare, Epic and Legendary (but there is no ethereal unlike items/equipment).
Meteorites can be enhanced to improve their effects and this is done by sacrificing other meteorites, flares and astral shards and can be enhanced up to level 5. The amount of EXP gained by sacrificing meteorites depends on the current grade of the sacrifice and the target. For example if you sacrificed a Poor grade meteorite into a Normal grade one the EXP gained would be less than if you did a Normal grade into a Normal one.
You can use Mass Enhance to sacrifice several meteorites of the same grade into the target.
Combining and Evolving
All Meteorites can also be evolved and combined to make higher grades.
To combine you need two max enhanced level meteorites of the same grade to use as material. Both of them will be destroyed to form 1 RANDOM new meteorite of a higher grade. For example: If you combined a Poor Attack meteorite with a Poor Defence meteorite you could get a Normal Evasion meteorite as a result.
To evolve you need a max enhanced level meteorite or astral shard and an astral shard of the same grade to use as material. Both of them will be destroyed to form the SAME meterorite or astral shard of a higher grade. It should be noted that the 2nd astral shard does not need to be leveled to evolve. Only the main TARGET needs to be maxed. For example: If you evolved a poor Attack meteorite with a poor unleveled astral shard you would get a Normal Attack meteorite as a result.
There is always a 100% success rate involved when combining or evolving.