Special traits are character only bonuses in Viking Conquest (not to be confused with traits).
If you already gained one, you can see it displayed in the Character screen.
There are 3 known special traits:
Dungeon Master[]
You will gain this if you put 7 or more lords in a single dungeon.
Congratulations! You've managed to imprison seven or more lords at (Location). You really are a true dungeon master (confirmed by multiple resources).
Bonus: reduces the chance of prisoners escape (?)
Skirt Chaser[]
You gain this if you have 5 or more love interests at the same time.
Congratulations! You've managed to make five or more women your lovers. Ladies must be heads over heels for you, so certainly you must feel proud to be in such a demand. Keep up the good work!(confirmed by multiple resources).
Bonus: +3 to relation with all lovers.
Wine Connoisseur[]
You gain this if you deposit 25 or more barrels of wine in your household storage.
Congratulations! You've managed to tuck away 25 or more barrels of wine in your household storage, a great feat considering you are in the part of the world more known for mead and ale. Either you have a drinking problem, or you are a true wine connoisseur.
Bonus: If you have wine in your inventory, you will be able to give it to lords for a relationship increase (there is a time delay of 4-14 days for each lord after which you can provide another gift). The increase depends on current relation with that lord (+1 or +2).
Tactics and usage of special traits[]
All three are somewhat marginal in usefulness compared to normal traits. Usefulness depends on your play-style though Wine Connoisseur seems to be the best for late game kingdom management where vassal relationship is highly important (though some caution should be taken as wine is also used for feasts). It is also the easiest one to obtain in perhaps 3-4 merchant trips to Dorestad while Skirt Chaser is a debatable hardest due to distances and not necessarily linear way of receiving quests from ladies/lords, while Dungeon Master could be obtained slightly easier in a prolonged campaign against 2-3 factions at once (with heavy troops and good battle tactics - shieldwall or if just keeping vassals close).