1. Yes. You will have a quest that will turn your entire party either Light or Dark.

2. In terms of gameplay, the Master and Ninja have different skill caps; the Warlock gets a certain bonus that the Arch-Druid does not; Liches lose two units of inventory space and are... well, Liches. Everything else is in the magic.

3. Light magic is much better for protecting and strengthening your party, while Dark magic is much better for offensive magic; thus, your Knight and Thief will benefit much more from Light than Dark.

4. There are only two real changes to the main story depending on which side you pick. The first will be immediately obvious, and the second will be at the very end of the game. Everything else is basically the same.

Just wanted to add, it's worth it, to check out both endings. If after finishing one, you decide that you don't want to replay the game to try the other, and likely would never do, then consider at least to load a game from before the good/evil choice, use and editor to give yourself god-like powers, and quickly do the other side's quest just to see the other ending.

By the way, only one was considered canonical, and later HoMM games were supposed to pick-off and continue from that ending. But that didn't happen, partly because HoMM fans didn't like the new story elements, and pretty soon the whole universe was rebooted so this all became a moot point.

Arch-Druid vs Warlock: What is there a non-spoilery version of the Warlock-exclusive bonus?

Lich: Why do they lose 2 inventory spaces? (Phylactery?) Which ones do they lose?

Completing the Warlock promotion gives you a permanent follower that increases the Warlocks' magic skills and does not count against your 2-follower limit.

Liches must keep a 1x2 Soul Jar in their inventory at all times, though it doesn't really matter where in their inventory.

Since so far I'm liking the magic option in a Knight/Thief/Cleric/Sor party, I'd likely go for Dark side first.

I'm also playing BDJ (Big Daddy Jim's) mod where completing a quest after being at max class promotion (like Arch-Druid or Lich) means characters can become another class. Still deliberating how to change the party, but that's a long way off.

I missed that because I didn't play a druid.

Do you have a screenshot by any chance. Or is there some video? I'm just curious what it looks like.

You can do the Warlock promotion quest even if you don't have a Druid in your party, as long as you have already done the Great Druid promotion quest. You'll still get the follower, even if you don't have any Warlocks to take advantage of it.

As for what the Warlock promotion quest is... well, you can get a few hints from some of the townsfolk in Nighon, even if you don't side with the Dark. To say more would spoil it.

That means that I did get the follower and never noticed it :(

Too bad I don't have any saves.

I'd really like a screenshot if anyone has one. If not, I'll try replay that some time.

I'll try to remember to see if I have a dark side save after I get home. In the meantime, I'll PM you.

Found something!

The guy turns in the quest at about 1 minute; I've set the video to start just before he walks in, so you can see his followers. The player exits the building just before 2 minutes, and you can see the familiar among his followers.

Excellent! Thanks.

Never knew about the Familiar. Interesting and neat.

What does this Warlock familiar do exactly?

Does the light side get a comparable bonus, and if so, what?