Spell Blast (Su) from Apocalypse Mystery...Combat Maneuver using???

[Lemartes]

Spell Blast (Su): As a swift action whenever you confirm a critical hit against an opponent with a spell that requires an attack roll, you can immediately attempt to bull rush your opponent in any direction. You don’t provoke an attack of opportunity for this bull rush attempt.

1. So do I use my regular CMB?

2. Is the size of the opponent limited to no more than one size bigger than me?

3. Can I bull rush more than one opponent as per normal?

4. Does enlarge etc. help as it normally would?

Thanks.

[Zwordsman]

1) yep because it doesn't say otherwise. (which is a bit weird)
2) It falls under standard bull rush CMB rules.
3) It is per crit. Crits require an attack roll. I don't know any spells that have 1 attack roll to hit multiple. But its per the crit, so only those you crit you get the bull rush. Off hand given the actual wording, you could only do 1/rd anyway.
4) Strictly speaking.. it would help as per normal cmb.

Overall though I think it is a bit of an oversight that it isn't CL+Cha or something simliar instead of straight cmb.

[Lemartes]

Awesome. Makes sense! Thanks. :)

[Pizza Lord]

I agree with Zwordsman. The wording would technically be your normal CMB with all things that modify it. I think it was probably an oversight and should be the CL + Cha modifier just like the Dust to Dust ability above Spell Blast. But that's going to be your GM's call (or your call if you're GM). Your size and other modifiers to CMB will still apply as will the size limit of your target based on your size.

[Diego Rossi]

As it is a Swift action, its use is limited to one opponent/round, even if you get multiple critical hits with the spell.