Codex of Outer Realms (3.5e Sourcebook)/Introduction

fundamentals

Outsiders are made up of ideals. That is the fundamental concept this book is based on. Devils are literally the concept of tyranny and oppression incarnate, demons are wanton destruction made flesh, and angels are good given form. this means that each faction of outsider not only belongs to its alignment, but is literally MADE from its alignment. Their version of physiological needs are literally just spreading the ideal they represent. Demons reproduce by creating wanton destruction, angels sup on the prosperity of mortals, archons shelter themselves in palaces of justice, and eladrin range on freedom and beauty.

Celestials

The Celestial races, such as angels, archons, eladrin and guardinals, are born from goodness, and thus try to spread goodness. in the mortal plane, this is pretty much just sponsoring the churches of good faiths, helping to set up orphanages, healing the sick, community aid programs, etc... While on the planes, they take a much more active approach. This includes trying to forge alliances and using diplomacy to spread their ideals, spreading wisdom and education, sustainable inter-planar commerce, or even just spreading hope to those in tough times.

What this means is that angels do more than fight evil/look pretty. They actually venture out to make the world a better place, even though that is generally a lot more boring than you'd expect. I mean seriously, you cant just go around slaughtering every bad guy you see and assume things automatically fix themselves, just look at any time someone tried to depose a dictator without having any form of backup structure. You end up with a power vacuum filled by terrorist and warlords.

Celestials aren't there just to stab the demon lord and pose for a photo shoot. They are there so those living under the evil empire or those terrorised by raving war bands can look forward to a future where they can live a good life, where they and their families don't have to worry about some dragon coming in to eat their daughters and can just focus on living their lives to the fullest.

Fiends

Fiends are evil. while they often have motivations beyond just evil, such as gaining wealth or influence, their "biological" imperative is to do evil, in the same way most living things have the biological imperative to reproduce. while celestials would work to make the world a better place, fiends work to ruin it; whether by actively causing damage or simply using their influence to cause societies to rot from the inside out.

while celestials would try to spread charity and opportunity in a settlement, fiends would directly destroy assets and try to promote crime. They are the ones whispering in the ears of tyrants, replacing a beggar's coins with knives and drugs, causing untold suffering just to empower themselves. but you probably already knew that the fiends were the bad guys.