There are several Easter Eggs throughout the game, some are just part of the gameplay, others can be abused to gain extra power.
Hidden Qualis Gems
There are 2 Qualis gems that can be found in the game.
The first gem can instantly be found in a hidden chest at Rane.
The second requires one gets a map to a "hidden Red Brotherhood hideout " from asking for rumors at a tavern. The hideout can spawn anywhere, and the first time one enters it, it will have a Qualis gem in another hidden chest.
Gambling Qualis Gems
This is a feature added to help the player in the early stages if they were having some troubles. To enable it, the player needs to have a Qualis Gem in the inventory.
After getting any guildmaster quest, if you return to the guildmaster and say you cannot complete the quest, he will offer you the chance to gamble a Qualis gem, and will give you some elite troops regardless of whether he wins the gem or not. You will still have to do the quest, however. Please note, after 2 tries, you will always lose your Qualis gem and it is no longer based on chance, but the troops are still obtained.
The troops you can obtain can be seen here: Gambling Qualis Gems.
Ordis - Rumor Easter Egg
If you ask Ordis or any traveler for a rumor for 10 denars, there is a chance he talks about the Vanskerries hailing an enigmatic god called a Saxon Dragon, a nod towards the mod's creator "saxondragon".
Adventurer's Wound Easter Egg
One of the dialogues the player gets when they get a job from one of Pendor's travelers to heal someone mentions that the patient is an adventurer who recently got struck in the knee by an arrow, and that they might have already given up their adventuring days to become a guard. This is a clear reference to The Elder Scrolls V: Skyrim, in which guards often say "I used to be an adventurer like you, until I took an arrow in the knee."
Schwarzenegger Quotes
When dealing with Mystmountain Raiders, they will often threaten the player before engaging in combat, often saying that they will ram their fist into the player's stomach and rip out their spine, or that they'll crush the player's people, see them driven before them, and hear the lamentation of their women. These are direct references to quotes from movies that Arnold Schwarzenegger acted in.
Alaric von Brouhaha
Upon capturing the Rebel Peasants faction's leader, Alaric von Brouhaha, one of the options when you talk to him is to unlock Custom Knighthood Order Unlockable Equipment, upon doing this, a message saying "Congratulations, you have found an Easter Egg!". The item unlocked is Torch.