Yes mr.Sut I would NOT like to tell you what he was all about but since you insist then allright.
Maul was not an ordinary apprentace. He was CREATED to fight the Jedi, and he was created to destroy them. He was what you would call an efficient "fighting machine". That's what made him not to be a real lord of the sith. He couldn't think for himself. Because there are always 2 lords. However he wasn't one. Now, Dooku was a Lord. He joined the Dark Side willingly, because he wanted to be more powerful than any Jedi. However during Ep2 we already see how Dooku wants to take out the Emperor and rule instead of him. That is when he asks Obi-Wan's help for them to destroy the Sith. Because a real apprentace always wants his Emperor's power (that's why Vader wanted Luke to join him, so they could kill the Emperor and rule together). Now back to Darth Maul. As I said he wasn't an ordinary apprentace. He was there just to serve the emperor and destroy the Jedi. Basically you can call him an extended arm of the Emperor. That's why he had the line "At last, we will reveal ourselves to the Jedi, at last we will have revenge". It's like the Jedi did something to HIM. Basically he didin't have to have any more lines than the 3 he has, because his look and movement explained how he felt very good. The half battle scene where he is cut off from Qui-Gon explains it the most.
Basically, you are not supposed to find out more about him, because THERE IS nothing more about him to learn. He was a fighting character, Dooku was a diplomatic character, however Dooku was able to think for himself. Dooku was the one joining the people of the Republic into the rogue groups that would eventually destroy the Republic. If you see Maul in his place, then well, hats off to you for the imagination. And again, Maul wasn't a human or any other creature. He was LITERALY a Sithspit.
I hope that clears it up somewhat for ya.
There are only two constants in this world.
1. I kill you.
2. You cry for a lightsabre damage nerf.