Call of the Vigilant
The Earthdawn system works through Step Numbers to determin what you roll to see if you succeed at something. Unlike d20 games where you roll a d20 plus a modifier, in Earthdawn you roll a set of dice which should average your Step. I’ll supply a table to everyone so you don’t have to guess what dice you need (It’s on page 14 of the player guide too). These numbers get worked out on your character sheet so you don’t need to do algebra in combat. Well, any more than in any other game system.
The Step you use is usually an Attribute Step + a Talent Rank. For example, a novice warrior has a Dexterity Step of 5 and a Melee Weapons Rank of 2. His Step to attack someone in Melee is 7.
Now a novice Warrior tries to hit his opponent. His attack Step is 7, so he rolls D12 to see if he hits. He rolls an 8, which happens to beat his opponent’s defense of 6, so he hits.
Now suppose the same warrior has to attack a ridiculously agile opponent with a Defense of 13. You might be tempted to say he’s screwed, but he still has a non-zero chance to hit because in Earthdawn, dice explode. What I mean by that is if a dice maxes out its roll (i.e. rolls a 12), he can reroll it and add to the total (So if he rolls a 12 on his D12 and rerolls to get a 3, his total is 15 which beats the 13). Dice can explode multiple times to keep getting higher totals. So his odds aren’t good, but there is at least a small chance.
A more experienced Warrior tries to hit with an attack step 11. He rolls D10+D8 and adds them up. As the step gets higher, you get more dice to roll. Any of the dice involved can explode. He should hit someone with a defense of 11 about half the time, as his dice should average 11.
If all of the dice you roll are 1s, the test fails, no matter how many dice you roll. This is called the Rule of One. It doesn’t come up all that often since you usually don’t roll high enough to succeed if you roll all ones with a small number of dice. This mostly affects obscenely unlucky massively skilled characters.