I will tell you what my army can do- especially sub-factions and artifacts. I will not tell you how I will use them. If you are a new player I will make sure to point out what could end up being gotchas in the first couple turns- I expect you to remember by turn 4. This game rewards system mastery- which includes what other armies do. I certainly can't remember everything that every army does, but I do know the key units and tactics for most armies. I do not want my opponent to tell me too much info about their army. I have found- for me- that the surprise of it happening in game, regardless of whether it causes a loss or not, is more effective as a way to remember what that unit/rule does. All of this applies to matched play only of course.