Breather Level: The Delaware mission in The Warchiefs. You don't even need to go straight away to the first mission, you might even be more interested in exploring the map and getting the treasures, because you're going to need them later. Not to mention that at some point of the exploration, you'll get a Courier Des Bois (a french settler) who can get the supplies scattered across the map for you. And later you'll find a Huron native settlement where you can build a trading post so you can get even more units, which will also come in handy for destroying the ships which hold even more units. You can even get some decent artillery units before doing the first mission. By the time you're finished with the side missions, an otherwise difficult mission becomes piece of cake, and you can get a big army with just a few resources.
Complete Monster: Sheriff William "Billy" Holme is the Big Bad of the Shadow section of The WarChiefsExpansion Pack. Initially a friend to Chayton Black, Holme becomes consumed by greed when gold is discovered in the Black Hills. Holme summons his old friend Chayton with the intent of manipulating him into kicking the Sioux off the land so he can claim the gold. When Chayton attempts to negotiate with the Sioux leader Crazy Horse, Holme follows Chayton and attempts to assassinate Crazy Horse, shattering any chance of a peace settlement. When Chayton builds a fort for Holme, Holme orders Chayton to destroy an entire village and leave no survivors—including women and children—even though they have done nothing. When Chayton protests the order, Holme initially tries to justify it as they will do something, and then dares Chayton to turn on him. When cornered by Chayton in a cave, Holme justifies all of his crimes by arguing he would have been rich. When Chayton asks Holme if he would kill the settlers, he admits the only thing that matters is the gold. When urged by Chayton to surrender peacefully, Holme attempts to shoot him with a pistol despite his life being spared. A man who uses his sheriff's position to manipulate his friend into murdering innocent people all for the sake of greed, Holme shows the dark side of colonization and settlement in a game that skirts around these issues.
Crazy Awesome: Some of the cheat units are this, like George Crushington, the giant titan-bust thing that spits torches at buildings and attacks by headbutting units, complete with comic book noises and graphics, or the Monster Truck you can use to flatten entire armies and colonies in seconds.
In an AMA at the Age of Empires 3 Heaven forums, lead engineer Sandy Petersen defended the game's focus in American colonization claiming that it would be ridiculous to play as Napoleon, start with a town center and build from there to fight the Battle of Austerlitz. Cue the first big game mod Napoleonic Era, whose aim is pretty much that.
Mis-blamed: No, this game didn't kill off the franchise - although as noted below, it was seen as falling short in comparison to previous installments, the real reason for the franchise's death was the closure of Ensemble Studios, for reasons unrelated to this game.
Moral Event Horizon: In Shadow, Chayton was tracking down Crazy Horse in an attempt to negotiate peace between the Sioux and the settlers. Holme trails him and attempts to assassinate Crazy Horse, completely wrecking any chance for peace between the settlers and the Sioux, so he could take the gold from the Sioux.
And yet Chayton continues with Holme even after that. It's only when Holme tells Chayton to slaughter a Sioux camp "before it becomes a problem later" that he finally switches sides.
In the Spanish version, the actress playing the terrified colonists fleeing the Cherokee in "Ice" got a little too enthusiastic in her role.
Politically Correct History: The game covers the entirety of the Colonial period, but slavery is scarcely even hinted at. All of the European factions can build plantations, but white settlers work on them. The fate of the many Native cultures is also heavily sanitized. While these topics could have been covered tactfully, Ensemble Studios decided to omit them altogether to avoid any controversy. Somewhat justified, however, since this is actually quite common amongst most games.
Actually, if one looks closely enough, they will notice that some of the European settlers have dark skin. So technically, slaves are present, but they intermingle freely with the white settlers and do the same things as them.
Campaign protagonist Amelia Black is another example: she is an unmarried half-Native American woman who runs a powerful company and wears pants, something highly unlikely in 1817.
The way the campaigns mostly disregard History, introduce completely new factions that are not playable otherwise in the game, and basically dance painfully as to not make any of the playable factions come across as Acceptable Targets. Except for the Circle, you will either eventually ally and fight together with every civilization you fight against at first, or you will be told that the enemy has been misled into fighting you and is not actually into it, like the Caribs in "Blood" and the Russians in "Ice".
Holme may be an Omnicidal Maniac and the white villain of a campaign about the Sioux Wars, but he isn't racist. The blood of the Indians and the Settlers is the same color, as he puts it.
The Scrappy: The Aztecs. The more historically-minded players hate that they are a playable faction, even the ones that can accept Iroquois and Sioux (in that order). They are out of time, out of place, and their technologies, infantry and naval units are nonsensically powerful in order to make them stand a chance with industrial powers, despite their main claim to fame being falling quickly to an archaic (by game's standards) army of Europeans. Even then, they are still hard to master because they can neither create their own cavalry or artillery. What seals the deal is that the Aztecs already had their time to shine as the stars of the The Conquerors expansion of Age of Empires II, and that unlike other civilizations carried over from the previous game (the Spanish, British, French, Germans, Ottomans, Chinese, and Japanese) they are stuck with the same fighting style, so they feel like treaded water. The studio elevating them to playable faction instead of other cultures that did survive the first Spanish onslaught and fought back to some extent historically, like the Inca, Maya and Mapuche, comes across as pushing them down the players throats.
Scrappy Mechanic: Most players avoid naval-oriented maps altogether due to Arbitrary Headcount Limits on each ship type and the incredible strain watching a naval battle puts on most low-to-middle-end computers. A later patch fixes the performance issues with naval units, but the mortar/monitor/rocket shell explosions will still put a strain on low-end PCs.
Sequelitis: The general consensus among fans is that III fell short in comparison to the previous installments.
They Wasted a Perfectly Good Plot: Using entirely fictional stories backdropped to historical events instead of entirely historical campaigns like the previous games. Especially glaring is the ample material in North American history from the time period used in the game. This does not apply to the second expansion although it does take a few liberties with things (i.e. the Chinese being the first to discover America and erasing proof of their presence.) This is especially egregious considering that the first two Age of Empires games had several campaigns, all based on real historical events.
The first expansion had Nathaniel Black, son of John Black, as the main character of the "Fire" Campaign (which revolved around the Iroquois), and Chayton Black, the son of Amelia Black, as the main character of the "Shadow" Campaign (where you played as the Sioux). Considering the expansion pack introduces 3 new civilizations, as well as the fact that we didn't learn anything about John Black's father Phillipe in the first game, you'd think they'd have him be the main character of a campaign where you played as the Aztecs (the third civilization introduced) to complete the trifecta, but nope.
Only the Sioux, the Japanese, the Chinese and the Indians are actually playable in the campaigns. For everything else, it's either the Knights of Malta or the Black family. Special regards go to the Portuguese and Dutch, who don't even show up as enemies in the campaigns.
Many of the European empires present in the game actually interacted with India, China, Japan, and the rest of Asia quite a bit during the time period covered, but you wouldn't get that idea from the Asian campaigns beyond the British in India.
The decision to make the game about American colonization, first and foremost. Imagine how different it could have been if that central role had been given to Old World conflicts with names as suggestive as The Thirty Years War, The Eighty Years War, or the Polish Deluge.
The lack of any official Expansion to cover Africa, which had plenty of European colonization and interaction within the time period covered. It is the subject of some fan made expansion, like the "Italy and Africa Mod" and The King's Return.
Unlike in previous games, you can't play games with more than two teams, nor have a skirmish game against an AI player using the same civilization as yours unless you make it in the editor.