I was just trying to find out more information about this game this morning, since I'd never heard of it before and it suddenly cropped up with people recommending it.
I thought this was interesting from the wiki.
"The system is based on the memory of the player; the player must speak the formula without reading it during the game. When the formula is correct, the spell is cast and the character loses astral energy points corresponding to the spell."
I wonder if it would get annoying though.
Well, that certainly is no longer part of the 4th Edition of DSA.
The game over the time started as very class focused, but nowadays, it is mostly a point buy system. I think the basic idea isn't too bad, either.
YOur initial build poitns can be used to buy ability points, race, class and region. This gives you some initial abilities like special skills (feats) and flaws and perks. So far, so well. Now, based on your mental abilities you also gain adventuring points (experience points) which you can use to improve talents and special skills, and spellcasters also their spells.
In game, talents are denoted with 3 ability scores. You roll 1d20 for each score and try to keep under or equal the score. If you fail, you can use points from your talent value to compensate. Remaining skill points are sometimes used to determine effectiveness of a skill attempt.
If you advance, you can spend experience points to improve your skills. The cost for improving a skill vary depending on skill, and (at least with optional rules) also depend on how much training you get.
(Melee) Weapon talent points have to be distributed (once) among attack and parry. You roll a d20 against a value determined by your ability scores plus your attack value and try again to keep under. Enemies can parry (usually once per round) if you hit and negate the damage.
(One think I always liked conceptually is that your "courage" attribute is also factored into the attack). Weapons grant weapon modifiers to attack or parry (or both). (Which is a simplification of an older weapon comparison system in previous editions.)
Shields work similar to parry, but are not the same. They grant their own bonuses and are not based on weapon talent but on special skills.
Ranged attacks are against a similar determined attack value, plus a modifier based on range and size. (Annoyingly enough, attacking a medium size attacker causes already a penalty, just for guaranteed extra math, err... probably weapon balance.) Loading most weapons takes a few rounds. (No Rapid Shot/Twin Strike Rangers in TDE)
Damage is rolled with a number of d6 and a bonus depending on weapon and your strength score.
You have hit points that increase only very slowly (not the D&D ablative hit point model) and if you take too much damage, you also suffer wounds for further penalties. Armor reduces damage taken.
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My opinion of the system overall: Hate.
The skill system is needlessly overcomplicated. Rolling 3 dice against 3 different "DCs"? Gargh. And checks with modifiers? Substraction is not only the least precise mathematical operation to perform on a computer, it also sucks in pen & paper games.
Combat? Armor is King. Shields, Parries, it's mostly useless. You want to attack, hit hard to break through every armor you find, while being heavily armored. It might be realistic for some values of realistic, but it's dull and unbalanced. The special skills for combat are complicated (attack with a penalty, if you fail, you take a penalty to your parries to the next round, and if you hit, you might get a chance to do something... I suppose there are some killer combos hidden in there, but I just can't bring myself to care finding them out.)
And overall 15 minute adventuring days seem likely in TDE, too, especially since the astral points (think mana points) regenerate slowly, and the same at least used to apply to the divine classes... (I remember that 3E TDE priests had serious problems recovering their points. One of the best ways to gain them back was by converting others to the 12-Gods belief system. Unfortunately, everyone already believes in that, except Orcs and a sect believing in a single god, and you wouldn't really want to try changing their beliefs!)
I suppose on the Retro/Stupid/Pretentious diagram, TDE moved over time from Retro to Pretentious.

The system "stole" a lot of concepts from other games. That's not necessarily bad, but it didn't do it always (or at all?) in a good way to make the game more stream-lined, faster or balanced.
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The world is a different matter. Aventuria is the size of Eurasia, approximately, with a lot of different and interesting cultures. There are other continents, and the world "Dere" (an allusion to "Erde", the German word for Earth) is as big as ours with same number of continents.
The backstory had the recent human population being settlers from a different continent. Orcs were the origianl population but have been driven out of their homelands. (Orcs in TDE are also called "blackpelts", so they are not the green-skin Orcs of Warhammer and D&D)
Elves and Dwarves do also exist, with different cultures.
The primary belief system is a polytheistic system of 12 gods and a 13th, "The Nameless". He might be evil or not, but it is said finding out his name and speaking it might be catastrophic (IIRC). There is a second system with only one god that only one country/culture believes in. And furthermore, there are also Druids believing in gods the other religions might consider either false or dead.
The world is richly detailed. I think it is a beautiful world, possibly similar detailed to how Forgotten Realms was (or more), yet without all those overpowered NPCs

.
Unfortunately, I also feel as if I didn't know enough about the world to do it justice, and the things I know about it make me feel as if it is not an adventuring place for me. I think it lacks the "Points of Lights" feeling a lot.
There are a lot of adventures available, some good, some bad. They are aimed for different ages, and some of them work fine without any combat and are well suited for beginning players (at least for the Germans view on violence

)
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My opinion the world is not really negative, though I just can't see myself running a campaign set there. (Playing in one is a different matter, the DM can do what he wants, though I still don't like the system.)
A highly detailed world is a weakness for me usually, but it might not be for others (obviously, it's not for the German fandom of TDE). I sometimes feel it is a little too... "soft", at least in the way the adventurers are written. The typical assumptions seems to be heroic, yet naive, good-aligned adventurers trying to make the world a better place. Except the naive, I can live with everything, but the naive irks me. (If any TDE fans are here, they might disagree with my description...)
I would find the system less "naive", if stuff like religious conflicts would seem more prominent, or if the relationship to the Orcs was more interesting. As it stands, the Orcs are evil, not rightful owners of the region the humans are now occupying...
Well, I am not an expert on TDE, so maybe this is sometimes discussed, but it doesn't feel like it is.