Here is an example of the OGL Ancients combat rules, as I understand them. I will focus on new rules presented in this book, and briefly mention those that do not differ from core d20 rules (e.g.: initiative, BAB, etc). Since I am also new to the rules, please point out any mistakes I have made in my interpretations.
Diem, a novice Hoplite (Warrior-4) travels from the Greek City state of Sparta.
He has traveled to the isle of Crete to battle the legendary Minotaur. They face off on the rocky ground outside his layer.
Diem, wins initiative and goes first.
Since he is a Spartan, he has a base speed of 40, so he easily closes with the Minotaur and attacks with his spear. He rolls a 12 on d20 to hit.
He adds his Base Attack Bonus (BAB) of +4 and his Str bonus of +2 for a total of 16.
It is the first regular turn in the battle, and the Minotaur has not yet acted, thus he is flat-footed.
We now see if this attack roll gets past the Minotaur’s passive defence. Passive Defence represents how hard it would be to hit someone who does not actively defend himself. Passive Defence is always = 10 +/- size modifier. Thus the Minotaur has a 10 –1 (large) = 9 Passive defence.
Since Diem’s to hit score is > than the beast’s Passive Defence, he has scored a ‘potential’ hit.
The Minotaur now gets to make an Active Defence (attempt to dodge the attack). This is a free action. Active Defence is a d20 roll + Dex modifier (reduced for armor) + misc.
The Minotaur has an Active Defence bonus of +0 (no dex bonus), and rolls a d20. He gets a 15.
Not enough to beat Diem’s attack score of 16. The Spartan scores a hit!
(Please note: attackers and defenders will probably roll their attack roll and Active Defence at the same time – thus speeding up combat).
Diem rolls for damage: The spear is 1d8. He adds +2 (str) for a total of 6 damage. The minotaur has no armor, so the damage reduces his hit points accordingly.
Now, it is time for the Minotaur to take a full-attack action and swing his Labrys (2-headed axe) twice (+9/+4 melee) and gore (+4 melee).
Our hero, Diem, has a Hoplite Shield, but has to make a crucial decision:
Anyone with a shield can elect to use the shield instead of his Active Defence. Unfortunately, you only get ONE Shield Defence roll per round (more for high-level fighters). While this is a free action, you must designate which attack you will try to block BEFORE the opponent makes his attack roll.
(There is a feat that will allow you to ‘see’ the attack roll first, before committing your Shield defence roll).
Diem decides that the Minotaur’s first attack is the most dangerous, and thus elects to use his Shield against it.
The Minotaur rolls an 11 on d20 to hit, + 9 BAB for his first swing = 20.
Diem has a Passive Defence of 11 (med sized vs large) and thus is ‘potentially struck’.
Diem now rolls his Shield Defence, which is similar to a melee attack bonus, as it gets better as he gains levels. He has a Shield Defence Bonus of +2 for being a 4th level Warrior. To this he adds his Wisdom bonus (+1) and the shield’s Coverage bonus (+5 for the Hoplite shield) = +8. He now rolls a d20, just like the active defence, rolling a ‘13’, for a total of 21.
He beat the attack roll of 20, and thus blocks the first axe swing! The shield is struck, and all the damage is applied to the shield.
The minotaur’s axe does3d6+3, and the total turns out to be 15 points of damage! The Hoplite shield has a Damage Resistance (DR) of 5 and a Damage Absorption (DA) of 6 against slashing weapons. Thus, the first 5 damage are resisted (ignored), and the next 6 damage are absorbed by the Shield (the Hoplite shield has 30 hp).
But unfortunately, the damage exceeded the DR and the DA in one blow, thus the shield is breached and destroyed. The excess 4 points of damage gets through to attack Diem’s body.
Lucky for Diem, he is also wearing armor. He is wearing a Bronze Corselet and a Corinthian helmet. In OGL Ancients, not only does armor reduce damage, it has a coverage rating that gives a guideline on how much of your body is covered by the armor. The Corselet has a coverage of +8, and his helmet gives an additional +1, for a total armor coverage of +9. Diem now rolls a coverage check (against DC 20) to see if the blow hits an armored part. He rolls a 5 on d20, and adds his coverage rating of +9. Not enough to make the DC of 20, and thus the blow lands on an un-armored section of his body. He reduces his Hit Points by the 4 remaining damage from the axe.
The Minotaur will take his second swing with the axe. Diem’s shield has been destroyed (even if it wasn’t, he has used up his only shield parry…).
He swings and rolls a 2. Adding his BAB of the 2nd attack will give him a total of 6. This is not even enough to get past Diem’s passive defence and is a complete miss.
Finally, the Minotaur uses his Gore attack. This time he rolls a 14 + 4 (BAB) for a total of 18. A potential hit. Diem rolls his Active Defence. Unfortunately, his armor has reduced his Dex bonus to +0 (heavy armor has a price!). He rolls a d20 and gets a 9. This is < the attack roll, and is thus a hit. (Poor Diem could not dodge this one...)
Diem sees if this gore can be stopped by his armor. Once again he tries to beat the DC of 20 with his bonus of +9. He rolls a 13. Adding his +9 = 22. The gore has struck his armor.
The gore does 1d8+6 damage, for a total of 10 (piercing damage from his horns). Diem’s Bronze Corselet has a DR/DA of 6/2 vs. piercing damage. 6 points are ignored, while his corselet will take 2 (reducing the HP of the corselet from 60 to 58 ). The 2 remaining damage is applied to Diem’s Hit Points.
(Please note: that un-like shields, armor that gets breached is NOT destroyed.)
With no shield, things may get tuff for Diem in the next few rounds…