Magical Essences can be acquired in two ways: a merchant or Salvaging. Merchants only sell skill level one essences so if you need a better quality essence, your best bet is to either search the AH or find a Salvager.
The two tables below show how the essence name associates with the required skill level and their rarity. Also, you cannot use Echoes and Whispers while creating a talisman - you must combine them to produce a rare quality essence.
|Essence||Rare||5 Whispers (50 Echoes)|