|Applying BtB Surprise Rules|
NOTE: I've been thinking about this stuff a lot recently (2018, 6 years in the future of this post) and have done a new post on surprise over here. This post is for historical interest (if that).
When two groups (of one or more figures) come suddenly upon each other there is a chance that each will be surprised. Normally, each side rolls 1d6 and a roll of 1 or 2 indicates that they are surprised as a group for 1 or 2 segments. A roll of 3 or higher means that they are not surprised. Do not subtract the different sides' dice from each other (as suggested in the tables in the rules).
If A rolls a 2 and B rolls a 3, A is surprised for 2 segments and B is not surprised at all
That's the basics of the most common case of surprise. The first modification is that characters with high (16+) dexterity scores will be surprised for less time than the die indicates and those with low (5-) scores will be surprised for longer. However, low dexterity never causes an unsurprised character to be surprised. If a member of party B has a dexterity of 4 s/he is still not surprised. However, such a character in party A would be surprised for 4 segments since party A is surprised.
A character in party A with a dexterity of 17 or more will not be surprised under normal circumstances as their dexterity reaction modifier means that even a roll of 2 will be reduced to zero.
Note that any encumbrance level above "unencumbered" negates all dexterity bonuses to surprise (but not penalties, of course). If you want your character to be like Errol Flynn's Robin Hood, s/he'll have to dress like him.
During surprise segments any character or monster who is surprised can do nothing beyond defend normally (ie, there is no to-hit bonus during surprise) while those who are not surprised may attack as if each segment is a full round.
If both sides are surprised then they simply gawp at each other for the required number of segments until one or both of them snap out of it. Thus if side A rolls a 1 and side B a 2, then there will be one segment of mutual gawping and one in which side A can act against side B as if the segment were a full round.
The next modification is that some classes and monsters are more stealthy or more perceptive than others, modifying their chances to surprise or be surprised. Rangers are an example of both - they surprise on 1-3 and are surprised only on a 1.
However, a group only rolls one die for surprise and the value used by their opponent is that of the least stealthy member of the group, so a normal party with a single ranger surprises on a 1-2 just like any other. On the other hand, a group is surprised as easily as its most perceptive member so the same party is only surprised on a 1 because of the ranger's presence.
When dealing with more complex examples, it's best to convert these modifiers into bonuses and penalties. Thus a ranger surprises at +1 (making a roll of 1-3 surprise) and is surprised at -1. If two rangers meet then these cancel out and both are surprised on 1-2. Elves in natural surroundings surprise on 1-4, which is +2. So if an elf and a ranger meet the elf is surprised on 1-3 and the ranger on 1-3 as well.
Being surprised is deadly. The rules consistently speak of "surprise" and "total surprise". As such, you may want to consider ruling that two segments are the most surprise that a group can roll (individuals can still get more due to low dexterity). This also allows you to use modifiers to surprise without increasing the chances of a massacre too much.
Talking of "deadly" - the rules say that missile weapons fire at three times the normal rate in surprise segments if they are ready. Yes, that's 6 arrows per segment (1 per second!). I don't know anyone who has applied this rule in real life as a blanket case, although it can just about work if you're very, very strict about what being "ready" means. I recommend ignoring it.
Some characters and monsters don't use d6 for surprise. The monk goes a bit further down the weirdo route and starts off with a d6 and changes to percentile. Handling these cases is fairly straight-forward (apart from the monk) if you use the idea that anything that doesn't surprise (or be surprised) on 1-2 has some sort of bonus based on this norm.
To take an extreme example, a ranger encountering a green hag (MMII). The hag surprises on 1-5 on d6 and is surprised on a 1, on a d20! We translate those values into +3 and -1 as above; the ranger is on +1 to surprise and -1 to be surprised.
The net result is that the ranger is surprised on 1-4 (2+3-1) on d6 and surprises the hag on 1-2 on her d20.
|Several Surprise Monks|
First level monks are surprised in the same way as anyone else; above 1st level there is a decreasing chance that they are surprised for one segment. I rule that monks simply can not be surprised for more than a single segment by anything as one of their special abilities.
That's it for surprise, next up is the main initiative rules.