[quote=@Indrajita]
Lol how does one know that hey I'm this Class and gets a feel of their abilities?
[/quote]

The Adventurer Class knowledge will be laid out properly when the party find an [i]Adventurers Guildhouse[/i] and scan their crystals.  By way of the [i]Gift of the Crystal[/i], they will also get access to a magical emailing service too known as [i]Source Comm[/i], aswell as access to the [i]Contract Network[/i].  It's kind of a mix of Source magic plus technology.

As far reasoning regarding dicovering skills and abilities [@Zool]'s explaination is as good as any other.  The Source crystal in each adventurers hand links them to [i]The Wellsprings[/i], which connects them with Source; the energy that makes up all of existence.  It would make sense somewhat that they could dig deep and figure out their powers through instinct.

[@Zapdos] has cleverly set up discovery of Adam's abilities in advance of the fighting.  If your powers/character are more methodical and cerebral, I would suggest taking his posts as an example of how to figure things out.

Arthur is... unique lol, I'll just say that.  [@Goblinguy]'s set up is a lot different from anyone elses.

[@Teyao] posts of James' discoveries was a mix of instinct and accident, then logical processing.  Maybe try something like that?

There's a lot you can do, it just takes imagination and stretching of the rules.  I know you'll do just fine.

Also, I would accept 'Isekai magic' as an answer lol