Take the last few days of Beta and talk to the NPC's in Town and the Guilds. While the text on the character creation can give you a hint, it is not what it looks like at first.
I give you an example i found out myself:
Nald'thal The Trader (i hope i spelled it right)
Just going from the description on the character creation you might think this is the deity to choose if you mainly focus on crafting or playing a Merchant. The symbol is some ancient currency. Nald rules over the world of the living, and Thal keeps the realm of the dead.
This is actually the one you want to choose for your Thaumaturge. If you visit the guild in Ul'Dah you know why. Nald'thal is in fact 2 persons in one. Nald, the guardian of the earthly wealth and rich and Thal the guardian of the poor and death. Both together represent the aspects of a Thaumaturgs' spells and skills (light and dark your first two spells). The currency is a symbol of what you have to pay to cross over from live to death. You loose all earthly possessions.
I hope this gave you some ideas and encourages you to actually learn more about this world instead of just grinding guildleves. There is a rich and beautiful lore waiting for you to uncover.
PS: I did some testing with and without this guardian and as a THM or ARC, there are very obvious differences. Edited, Sep 16th 2010 8:34pm by KindjalFerrer Edited, Sep 16th 2010 8:34pm by KindjalFerrer