So, a group of Adventurers enters a large dungeon room to engage a group of Goblins (using the abstract movement you described). The Mage and the archer hang back. The mage casts an area-effect spell (fireball).
Does it hit all the goblins in the room along with the Adventurers engaging them? Does it hit some and not others? Does the GM guess where the combatants are positioned or is there a game mechanic for this?
Let's see...first I'd want to determine initial distance of the goblins from the party. I remember in many versions of D&D this could be randomly determined, and there's nothing preventing me from rolling some dice for this purpose. But I decide not to go that route, and rather state that the goblins are 50 feet away, all sort of within ten feet of each other (don't ask why ). First, I determine there is no "surprise round" because neither side were attempting to be stealthy. The players announce they are going to make goblin burgers for dinner, so I announce the beginning of combat. Let's say there are two PCs, one fighter type and one mage sort. Let's call them Baddeass and Wizawas (no, I'm not really this silly with names in my real games!).
ONE ROUND OF DEATH (with some movement):
Baddeass decides he wants to charge at the goblins, to beat them to death with his favorite yew club.
Wizawas is going to cast a fireball without regard to his friend's reckless charge, well, just because.
So, we go by phases, top Reflexes rank first (I'm going to ignore modifiers due to weapons in this example because it's late...
Baddeass is highest, with a Reflexes of D10. He pays no attention to his chanting mage friend, and charges ahead toward his stinkin' goblin foes, yelling something incomprehensible. His Speed score is also D10, so he can move 100 feet and still take an attack action. Yippee! He can run 20 feet per phase, so by Phase D6 he will have moved 60 feet (including phase D10). He would get his attack in but...
Wizawas' spell fires off in his initiative phase, which is D6. This places his charging friend within striking distance of the goblins. For area spells, the area-of-effect equals 2 × MRV of the relevant Power Source Specialization in diameter (add Mastery if applicable), with the point of origination at a distance of up to 10 × MRV of Power Source, in line of sight. SO, say our wizardly Wizawas has a Arcanum ability of D10 and a specialization in Primordial magic of D8. His fireball will be 16 feet in diameter, catching our poor fighter friend along with the goblins just as he gets near to them.
Wizawas rolls his dice, D10+D8, and gets maximum 18 threat points.
Say Baddeass has Resistance D4 ×2 + Willpower D4, for a whopping 12 points in his Resilience Defense Pool. Thus, the fire penetrates his Resilience DP, and he takes 6 points against his Toughness. Poor guy. He should have waited.
The goblins don't fare any better. I described them to the players as oddly huddled together, somewhat center of the room, all ten of them within ten feet of each other. So, because they are all fodder, and (let's say) none have passive hit points amounting to 18, they all die. What fun! Alright, if I were feeling gracious toward the little monsters, I could grant them high Speeds, like D10. Why? Because a character may use Speed to mitigate
Potential-Harm from an area-effect spell, provided there is reasonable room for evasion (as determined by the GM)***.
The mage blows the smoke from his knuckles and takes a nap...
*** When dodging area effects, the character must run
to some point outside the radius in any direction.
Movement in ERP is usually abstract, so the GM
must determine whether this is possible. A good
rule of thumb is to compare the spell’s radius with
the character’s Speed or Move Rank × 2. If the
speed or move score is equal to the radius, the
character can dodge to reduce damage. If not, he
cannot move fast enough to dodge. When dodging
missile weapons, boulders, or ranged magical bolts
no wider than 5’ diameter (all of which must have
some visible and tangible component to dodge), the
character must move at least 5 feet, or else half the
threat points automatically bypass the dodge DP.
PS: if anybody read the first version of this post, you may have noticed a math mistake. This note is to inform you that you were seeing things. It never happened.
...time to go to bed...