Multi attack isn't ranked. Rather, an attack gets the Multiattack property, which increases the attack's power point cost by +1 for each rank of the attack.
It has three options:
- You can attack a number of people in an arc, with a lowered attack bonus against each
- You can deal extra damage to one opponent (assuming your attack can damage them) based on how much you beat their Defense by
- You can provide 'covering fire' to give all ranged attacks a penalty against one character. Attackers can ignore this penalty at the expense of giving you a free attack against them.
See the d20Hero SRD's 'Modifiers' page for more details.
Single Attack:
To use a Multiattack against a single target, make your attack check
normally. If successful, increase the attack’s resistance check DC by
+2 for two degrees of success, and +5 for three or more. This circumstance bonus does not count against power level limits.
If an Impervious Resistance would ignore the attack before any increase in the DC, then the attack still has no effect as usual; a
volley of multiple shots is no more likely to penetrate Impervious
Resistance than just one.
Multiple Attacks
You can use Multiattack to hit multiple targets at once by “walking”
or “spraying” the Multiattack across an arc. Roll one attack check per
target in the arc. You suffer a penalty to each check equal to the
total number of targets. So making a Multiattack against five targets
is a –5 penalty to each attack check. If you miss one target, you may
still attempt to hit the others.
Covering Fire
A Multiattack can provide cover for an ally. Take a standard action
and choose an ally in your line of sight, who receives the benefits of
cover against enemies in your line of sight and in range of your
Multiattack. (You have to be able to shoot at them to get them to keep
their heads down or this maneuver won’t work.) You cannot lay down a
covering attack for an ally in close combat. An opponent can choose to
ignore the cover provided by your covering attack at the cost of being
automatically attacked by it; make a normal attack check to hit that
opponent.