Classes
Any of the classes in the SRD may be chosen: Barbarian, Bard, Cleric, Druid, Fighter, Monk, Paladin, Ranger, Rogue, Sorcerer, Warlock, Wizard. Important additional lore on the classes as they are in Ataland is provided below.
Druid
In this setting, Druids acquire their Wild Shape ability through the consumption of a potion known as Verdant Elixir. This potion must be quaffed monthly in order for the druid to maintain their Wild Shape capability. Failure to do so results in the effects wearing off within 5-7 weeks from the last dose, at the GM's discretion. If a non-druid imbibes the potion, they would be unable to control their wild shape - behaving as a wild beast. If this happens with a player, the GM should take control of them for the duration. Consequently, the recipe for the potion is kept secret, shared only among those deemed trustworthy enough to use it responsibly.
Sorcerers
Sorcerers are frequently the target of discrimination in Ataland. Many people believe that Sorcerers were responsible the destruction of Theyruse with their reckless use of magic. Regardless of the legend's veracity, Sorcerers are treated with mistrust or even outright aggression. This applies to all Sorcerers, but more so those who obtained their power from their Theyrusian blood.
This has made Sorcerers very rare as many who have the spark don't pursue it. Your local barkeep may be able to summon a small flame and you'd be none the wiser. Those that do choose to follow their gift can find work as adventurers or mercenaries.
When building a Sorcerer, you should keep this prejudice in mind and decide if and how it has impacted that character. Maybe you hide the source of your magic, or flaunt it openly regardless.
See also: History, Pre-Calamity - Year 0