These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Accidental Innuendo: It's jokingly rumored among the fandom that the reason for the High Men's change of name in the sequel to Archons is due to the original name's similar pronunciation to a certain component of the female genitalia.
Character Alignment: Ultimately a battle between good and evil with the neutral races playing wild card. In The Wizard's Throne, alignment is now determined by whatever the dominant alignment of your forces is, rather than by your own stats. During the Wizard's throne you cycle between good and evil and back again in an attempt to restore the Balance Between Good And Evil.
Designated Hero / Designated Villain: We're told that the Elves, Halflings and Dwarves are good, and the Orcs, Goblins and Dark Elves evil, but they don't play any differently. While the good races are described briefly as having peaceful wholesome habits and the evil races are supposed to be violent and aggressive, we don't really see this in action either. Finally, the Elves' goal is peace while the Dark Elves want genocide of the humans, but they want the genocide because the humans did it to them first. This kind of retribution doesn't necessarily fall outside the realm of what many "good" characters do. And in gameplay the difference doesn't show up at all: both sides are equally warlike, and have the option of fighting or buying off neutral races. Furthermore, a central gameplay mechanic is the ability to repopulate captured cities with a population of a friendly race; it's plain cultural imperialism at best and the good and evil races do this with equal impunity.
Never mind the fact that "good" races enslave the population of their enemies just like the evil ones.
The Highmen are even designated as "pure good", although it is hinted that they either exterminate or expel all other races (even the good ones) for the sake of a World of Men.
For what it's worth, the Goblins use suicide bombers and poison unlike their Good counterparts. There's a lot more violence if you look at the Flavor Text of their other units too.
Evil Is Sexy: Karissa, the female Wizard of Fire from the second game.
Game Breaker: In the first game, First Strike on a hero, especially when combined with Cold Strike or Lightning Strike. Whenever the you get attacked in melee, you get to attack first with a good chance at freezing or stunning the attacker, thus negating the attack. Or with high enough damage, just killing the attacker outright. With the Customize Hero option, this can be bought on a leader at the start of the game, thus leading to a One Man Party.
In Shadow Magic, you can create an inventory item with the Drain Will and Dominate abilities. A hero equipped with this is practically guaranteed to add any one enemy unit from every battle to your side, permanently. Even the ones supposedly immune to mind control. Even enemy heroes. That results in many players going into the nomads' third mission with a killer stack of 7 heroes.
The Chain Lightning spell in the first game can stun up to four enemies for a small mana cost, is very easy to target, and it's Friendly Fireproof.
Sacred Wrath, a spell that hits everything on the battlefield with holy light, becomes Friendly Fireproof in Shadow Magic. With enough casting points, it can be cast up to three times (more with well upgraded mage heroes), making for a very effective way to damage and debilitate a large garrison or strike force.
The spell Flood, given a couple of turns, floods every baseline ground tile with water. The aquatic Lizardmen are already at a strategic advantage on watery maps, but with this spell in play this advantage grows into absurd levels. Luckily for the other players it takes a long time to pull your research to this level.
That One Level: The first and third dwarf missions of the first game's campaign start you with few resources and run you through huge mazes of dark, enemy filled tunnels to reach specific points on the map. If you don't know exactly how to get to the goal, it's easy to either spread your forces too thin or get lost, both of which give the enemy time to build up strong forces undisturbed.