Update: This has been made into a 1 page 1D6 RPG system – blog link
I listened to ChgWiz’s (Michael Shorten’s) The Dungeon Master’s Handbook podcast about 1e ‘Surprise Rules’ and wondered if it could be converted into a simple combat system (or used for anything else); and why the Surprise Rule makes the DEX stat useful to non-thieves.

__Recap of the 1e Surprise Rule (as understood)__

This is how I understand the Surprise Rule in AD&D to work:

1. Roll for surprise if one or both parties might be surprised.

2. Surprise is like an attack roll, it’s your ability to surprise your foe (it’s __not__ like a saving throw, i.e. a chance to avoid being surprised). So the chance of being surprised is based on your __foe’s ability__. Personally, I think players should roll to surprise their foe and the DM should roll for the monsters to surprise the PCs (often it’s done the other way around).

3. By default the base chance to surprise anyone is a roll of 1 or 2 rolled on a D6.

4. But, some creatures are better at surprising; for example, Bugbears surprise on a roll of 1, 2 or 3 on a D6; and Giant Owls surprise on a 1, 2, 3, 4 or 5 on a D6. Wow, Giant Owls have 4HD, so they are in effect a bit like flying ogre ninjas.

5. This is the neat bit mechanically (at least I think so). The above roll not only determines if you are surprised (great), but __also__ gives the duration of the surprise. So, it’s doing two things with one roll (i.e. (i) determining if you are surprised and (ii) how long you are surprised for; and all in one roll).

The below table gives the duration of the surprise indexed to the die roll on a D6 for three creatures:

So, it’s a bit like the game “chicken”, the aim is to get as close to the maximum number of rounds without going over. So a roll of 3 for an orc is no use but for a Bugbear it’s the best roll.

6. Now for the wrinkles. Some classes can reduce the number of rounds they are surprise for. So, for example a ranger reduces the number of rounds they are surprised for by 1 round. This applies to them and to the group they are in. Therefore, the above table now looks like this when a ranger is present:

That is, the number of rounds has been reduced by 1 round in each case. So, a roll of 1 is in effect the same as not being surprised. Not surprised is shown in the blue region whereas the green region is where the time being surprised is reduce to 0 rounds or fewer (i.e. the PC’s reactions counteract the surprise).

7. More wrinkles. If a PC has a high DEX score they can get a RAA bonus, which again is used to subtract from the rounds they are surprised for.

So, if a thief with 17 Dex (RAA of +2) is in the above party (i.e. with a ranger in it) the table for the thief now looks like this:

So, this thief is in effect never surprised by Orcs or Bugbears, but for Giant Owls on a roll of 4 or 5 can be surprised, but for no more than two rounds. This gal has the reactions of a cat. However, a DEX bonus only applies to this PC and not to the group as a whole.

.*.. but, but*, why a roll of 4 or 5 on a D6 instead of a roll of 1, 2 on a D6 – same odds right? True, but under that system:

Thief surprised on a roll of 1 or 2

Party surprised on a roll of 1, 2, 3 or 4.

So, on a roll of 1 on a D6 means everyone including the thief is surprised for 1 round, but on a roll of 4 on the D6 the party is surprised for 4 rounds and the thief for none. So sometimes the thief and party are equally surprised or the party super surprised and the thief not at all. Seems illogical. Under the system explained above, the thief is always 2 rounds better off than the party no matter what the roll is (hence more consistent).

Sometime I feel like I’m torturing myself.

__Scenario 1__

Imagine the party describe above is swooped down on by silent Giant Owls in the dark. The DM rolls to see if the party is surprised (the owls are ambushing so they do not need to roll for surprise). The D6 is rolled a 4 comes up. Therefore:

The **party** is surprised for 3 rounds (4 rounds minus 1 for the ranger bonus = 3 rounds).

The **thief **on the other hand is only surprised for 1 round (4 rounds minus 1 for the ranger bonus and minus 2 for her RAA = 1 round).

__Scenario 2__

For argument sake, let’s say the party slips off a cliff and lands in a giant owl nest. This time both the owl and the party might be surprised.

A D6 is rolled for the party who get a 3 this time. The **party** is surprised for 2 rounds, except the **thief **who is in effect not surprised.

A D6 is rolled for the Owls who get a 2; so, the owls are also surprised for 2 rounds.

Net effect – everyone is surprised for two rounds, except the thief who gets two rounds of action. She of course decides to use her 2 rounds to make good her escape.

__Summary__

:: Mindset: Roll surprise like an attack. Players roll to surprise their foe and the DM rolls to surprise the party (i.e. on the monster’s behalf).

:: Surprise is a fun rule.

:: It also makes DEX a useful stat for non-thieves. Think of the acrobatic fleetfooted fighter that can slash a foe to death before their opponent can even draw their weapon. This can be much more useful than a +1 or 2 HP per level when buffing the CON stat. Likewise, a nimble unflappable magic-user who can get off a spell (or run for it) before the open-jawed orcs can say “whod dat?”. Finally, high DEX thieves become more effective (even deadly) in combat, perhaps even getting in the fabled back-stab while their opponent struggles open-mouthed to comprehend the threat. Worse still, a negative RAA can add time to rounds the PC is surprised for. In the reverse, a PC with 3 DEX could be surprised for a total of 8 rounds by Giant Owls on a roll of 5. I can’t see anyone surviving that kind of onslaught.

Wow… that ^ was longer than intended!

__Learning lessons / Repurposing AD&D surprise rules as a combat system__

I think I’ll save this post in full for another day.

But basically: you roll to hit by rolling equal or below your skill (like in Surprise). If you hit, you do that number of HP damage (like the rounds of surprise). If you have armour (or defensive magics), you can subtract units off the damage (like the RAA bonus).

E.g. a monster has a skill of 3, and they roll a 2 on a D6. They therefore do 2 damage. The PC is wearing heavy armour and so can subtract 1 off the damage. The PC therefore takes 1 damage. So, hit and damage is determined in a single roll.

Of course, a combat system like this needs proper scaling (e.g. PCs gain 1 damage per level, or can spend this on fighting skill, magic etc.). I have some crude ideas, and maybe I’ll pull my finger out and expand on this later.

– – –

Me on DriveThru; at the moment I’m mainly pimping my procedural:

:: High Seas ‘Hex Crawl’ – In the Heart of the Sea,

:: Wilderness Hex Crawl – In the Heart of the Unknown,

:: Dungeon/network generator – In the Heart of the Delve & Dangerous

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