Well, there is an easy way to find out every ending without playing through the game for each one. Download an Arcanum DAT extractor, and extract the ending slide narrations (you will find them under Sound\Speech\Slide). I will list them all, in order of the narration files, and include my best guess at the triggers required.
1.) Jongle Dunne formulates a way to turn lead into gold, after you supply him with ingredients, and becomes the richest man in Arcanum. [Pick up a package from Charles Dolan in Dernholm and deliver it to Jongle.]
2.) Because you destroyed the bridge materials in Shrouded Hills, Lukan controls access to the town, and it withers away. [Destroy bridge materials for Lukan the Witless.]
3.) Because you defeated Lukan and freed the ghost of Bessie Toone, the mine is reopened and a new silver vein is discovered. Shrouded Hills becomes a boom town. [Rid Shrouded Hills of Lukan and free the ghost.]
4.) Even though you defeat Lukan, you didn't free the ghost of Bessie Toone, and the mine is barren. Shrouded Hills withers and dies. [Rid Shrouded Hills of Lukan only.]
5.) Because you rid Shrouded Hills of Lukan and freed the ghost of Bessie Toone, the mine is reopened and a new silver vein is discovered. Shrouded Hills becomes a boom town, and because of the new sheriff Doc Roberts, it has no problems keeping the peace. [Rid Shrouded Hills of Lukan, free the ghost, and help Doc Roberts foil the bank robbery.]
6.) After the death of Gilbert Bates, his company shuts down. Appleby tries to meet the demand for steam engines, but the poor quality of his machines throws Tarant into chaos. [Kill Gilbert Bates.]
7.) After the deaths of Bates and Cedric Appleby, there is no longer a steady source of steam engines. Shortly the sewers of Tarant break down and electrical power systems fail. In a matter of months, Tarant is thrown into chaos. [Kill Gilbert Bates and Cedric Appleby.]
8.) Because of the death of Darian Maug, Pollock's gang is victorious in the Boil, and moves on to the rest of Tarant. Tarant quickly becomes shadowy and crime-ridden. [Kill Darian Maug.]
9.) Because of the death of Pollock, Maug Clan is victorious in the Boil, and moves on to the rest of Tarant. Tarant quickly becomes shadowy and crime-ridden. [Kill Pollock.]
10.) After the death of Pollock and Darian Maug, the Boil is renovated. The Bentley is rebuilt and becomes the most elegant hotel in Tarant. The owner, Caleb Malloy, is often seen mixing drinks in the hotel bar. [Kill Pollock and Darian Maug.]
11.) Don Throgg becomes a leading political activist for Orish rights. As a champion of equal rights, he establishes the right to vote for all citizens regardless of race or gender. He is elected to the Industrial Council, and eventually heads it. [Convince Don Throgg to end the orc uprising.]
12.) Maximilian returns to Cumbria, and is hailed as the rightful king. Cumbria becomes a powerful nation, adept in both magic and technology, and the Dragon Knights are revived under Lianna Pel Dar. [Speak to Maximilian on the Isle of Despair after speaking with Lianna Pel Dar, then return to Lianna and inform her of Maximilian’s fate.]
13.) Under King Praetor, Cumbria continues to decay and is eventually swallowed by the Unified Kingdom. [Don’t finish the Maximilian quest.]
14.) Because of your mediocre performance in the negotiations for Caladon's membership into the Unified Kingdom, there is war after only a few years. After many wars, there is no clear winner. [Don't perform well in the negotiations.]
15.) Because of your mediocre performance in the negotiations for Caladon's membership into the Unified Kingdom, in a few years there is war. However, because you helped Hieronymous Maxim, he is able to build an armada of airships, and Caladon wins the war. [Don't perform well in the negotiations, deliver the camera from the Zephyr’s crash site to Hieronymous Maxim.]
16.) Because of your excellent performance in the negotiations for Caladon's membership into the Unified Kingdom, Tarant prospers. Caladon never reaches it's full potential. [Perform well in the negotiations.]
17.) Because of your excellent performance in the negotiations for Caladon's membership into the Unified Kingdom, and Don Throgg's benevolent leadership, both Tarant and Caladon prosper. Peace reigns for many years in Arcanum. [Perform well in negotiations, convince Don Throgg to end the orc uprising.]
18.) The deception of the Panarii by the dark elves is brought to light. Alexander becomes the new high priest, and his experiences becomes part of Panarii lore. [Discover the true fate of Mannox and return to Alexander.]
19.) Because you convinced the mayor of Blackroot to rejoin Cumbria, there is a small struggle for ownership of the town. Maximilian is victorious, and under his rule, Blackroot becomes one of the most important port cities in Arcanum. [Convince Blackroot’s mayor to rejoin Cumbria, complete Maximilian’s quest.]
20.) Because you convinced the mayor of Blackroot to rejoin Cumbria, you seal it's fate. Under King Praetor, it decays and disappears. [Convince major to rejoin Cumbria, don’t finish Maximilian’s quest.]
21.) Because you fail to convince the mayor of Blackroot to rejoin Cumbria, there is a war between Cumbria and Tarant over ownership of the town. Maximilian leads Cumbria to victory. [Don't convince major, Maximilian’s quest.]
22.) Under the renewed leadership of Loghaire Thunder Stone, the Wheel Clan rejoins the world. He lives for eight hundred years, and becomes a hero to the dwarves. [Convince Loghaire to return to his people.]
23.) After the death of Loghaire Thunder Stone, he is regarded as a hero for his defense of Arcanum. His son Randver follows Loghaire’s example, and is a wise and benevolent leader. [Convince Loghaire to join you, and have him die?]
24.) Loghaire never returns to his people, and his son Randver takes an uncertain hold on the throne. The dwarves splinter, and there is a bloody war. Loghaire’s son eventually is victorious, but the spirit of the dwarves is broken. They retire from the outside world, and are never seen again. [Don't discover Magnus’ heritage, Loghaire to return to his people.]
25.) Loghaire never returns to his people, and his son Randver takes an uncertain hold on the throne. The dwarves splinter, and there is a bloody war. Magnus Shalefist, as head of the new Iron Clan, ends the war and becomes the new Dwarven King. He leads the dwarves to a golden age. [Discover Magnus’ heritage, don’t convince Loghaire to return to his people.]
26.) Loghaire never returns to his people, and after the death of his son Randver there is no obvious king. The dwarves splinter, and there is a bloody war. Magnus Shalefist, as head of the new Iron Clan, ends the war and becomes the new Dwarven King. He leads the dwarves to a golden age. [Discover Magnus’ heritage, don’t convince Loghaire to return to his people, and kill Randver.]
27.) The Bedokaan ally with the elves, and rid the forest and Dark Fens of those who would harm the land. The Bedokaan become civilized, and share the wonders of the new age. [Convince Kan Kerai that not all 'warm bloods' are alike.]
28.) The Bedokaan continue to live in the Dark Fens. They live the primitive life of nomad hunters, and never speak with the elves again. [Don’t free the elven hunter.]
29.) After Arronax returns to Arcanum, he buries his father. Then he raises Vendigroth from the wastes, and it becomes a place of awe and wonder. [Release Arronax and let him join your party.]
30.) The Bane of Kree returns to Arcanum, and amasses an army of barbarians. All of Arcanum unites to fight him, and are eventually able to stop him. You are held responsible. [Give Kryggird's Falchion to the Bane of Kree .]
31.) You take the title of Death's Champion on your return to Arcanum. The only survivors you leave are scattered groups hiding in the wastelands. Arcanum never recovers. [Based on your conversation with Kerghan.]
32.) You are revered as a hero on your return to Arcanum. Your name becomes nearly mythical. [Based on your conversation with Kerghan.]
33.) You take the role as a Just God on your return to Arcanum. You end the hostility between the races, and instill a sense of morality for all. You start a golden age, where both magic and technology are used to build a better world. [Based on your conversation with Kerghan.]
34.) You take the role as a Dark God on your return to Arcanum. The world becomes a dark and pain filled place, where men are afraid to speak their minds or follow their dreams. You are worshiped by all, but also hated and feared. [Based on your conversation with Kerghan.]
35.) You take the role as a Quiet God on your return to Arcanum. You fade into memory, but your example lives on, eventually leading to an enlightened age. Based on your conversation with Kerghan.]
36.) You are uncertain of what type of God you want to be. You wander Arcanum, while the world waits for your wisdom. It waits a long, long time. [Based on your conversation with Kerghan.]
37.) After your death, Kerghan returns to Arcanum. Arcanum is now nothing but a burned out shell, existing only in memory. [Lose to Kerghan.]
38.) Having joined with Kerhgan, you help him destroy all life on Arcanum. Once it is accomplished, Kerghan turns on you, a struggle you barely win. You are now waiting on the ruins of Arcanum, waiting for your end. [Choose to join Kerghan.]
39.) Lukan eventually found someone to destroy the materials for the bridge, and continues to control the only access to Shrouded Hills. The town withers and dies. [Fail to rid Shrouded Hills of Lukan, without helping him destroy the bridge materials either.]
40.) After the death of Pollock and Darian Maug, the Boil is renovated. The Bentley is rebuilt and becomes the most elegant hotel in Tarant. [Kill Pollock, Darian Maug, and Caleb Malloy.]
41.) After the death of King Praetor, Cumbria crumbles and is swallowed by the Unified Kingdom. [Kill King Praetor.]
42.) Because you convinced the mayor of Blackroot to rejoin Cumbria, you seal it’s fate. The town decays and is swallowed by the Unified Kingdom. [Kill King Praetor, and convince Blackroot’s mayor to rejoin Cumbria.]
43.) Without a strong king, the dwarves splinter, and there is a bloody war. In time the conflict is resolved, but the spirit of the dwarves is broken. They retire from the outside world, and are never seen again. [Kill Loghaire, his son Randver, and fail to discover Magnus’ heritage.]
Edit: I was in quite a rush before, now I've cleaned up the list and clarified it quite a bit. Also improved the spelling of various names.
