martedì 15 dicembre 2015

Six "20" between 19 and 21 an old school take on d20 to hit mechanics

Some retro-clones keep using to hit tables, one the reason is to respect the presence of repeated 20s in that tables.

The clones that respect the 6 20s in a row are OSRIC and Adventures Dark & Deep (although the second is much more than a clone) the two games most faithful to AD&D 1st edition (the one with 6 20 in a row). Labyrinth Lord has the row of 20 but the tables don't show any number greater of 20 and in the advanced edition we have even 7 20. The Rules Cyclopedia and D&D BECM instead has 5 20 in a row (so I don't understand why Labyrinth Lord don't emulate this).

Classic Table with the six "20"
attack value is dependent on class, Fighters get +1/level, Clerics +2/3level, Thieves +1/2 levels, Magic-Users +1/5 levels

Since Ad&d 2nd edition which adopted THAC0 and the d20 system the 6 (or 5) 20 in a row are no more.

Can the 6 20 in a row be implemented in games without tables?

The answer is yes.

Simulating the 6 20 in the "d20+bonus greater then AC" system

It can be done by considering the bonus from strength and magic (BoStMA for short) and adding 5 (or 4) to the roll if the d20 roll+BostMa is equal or greater of 20 or more simply it can be calculated the d20 range for which the +5 (or +4) bonus can be added.
The "threshold" is the number to roll on the d20 to get the +5 bonus

Example: Igor has a +2 for strength and +1 for magic the +5 bonus range would be 17-20.
Using normal rules of d20 (and all system that don't use tables) if Igor has a total bonus of +5 (+2 for level +2 for strength and +1 for magic) when he rolls to hit he will hit up to AC 20 with a roll of 15 (15+5=20), AC 21 with a 16, AC 27 with 17 (17+5+5), AC 28 with 18 and so on.....

As can be seen with such a bonus you will get the same effect of the 6 (or 5) 20 in a row

More trick from this system

A few things can be noticed:
1) this system (and the original tables) gave more importance to strength/dexterity, specialization and magic bonuses than newer system/editions (since with a +5 to hit from strength and specialization a 1st level fighter would hit up to AC -5/25 25% of the times)
2) since such low/high AC are not so common in old school game the advantage from this system go out of the window quite soon

So why not use the threshold from the above table for more effects?

Here some possibilities:
a) +5 to hit
b) +5 to damage
c) disarm
d) stun
e) additional attack

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