Arcane Focus
An Arcane Focus is an item used to better focus Aether while spellcasting. Most people require an arcane focus to use any kind of magic, although those who possess a only require them for high level magic.
Significance
An item must have a strong sentimental value to the caster to be used as a focus, and does not require any other properties, magical or otherwise. As a result a person's focus is generally unique to them unless the item represents a shared experience. A living creatures cannot serve as a focus, only an inanimate object. Typically it is something easy to carry or to wear as an amulet, although this is primarily for matters of convenience rather than requirement.
A famous arcane focus is a magi's spellbook from their time as a student.
Item type
Magical
Dimensions
It is recommended the item be easily portable, for the sake of convenience. Books and amulets are famous examples.