Again, not quite a buff
Extend Twin Repeat Maximize Empower: Abyssal Army(SpC)
(along with the usual Summoning buff feats)
2d4 Dretch, 1d4 Babau, 1 Vrock
Conjure yourself a small army of obedient demons to do your bidding for the next few hours, while you sit back and scry.
Persist would be a cool addition to this. And it sounds like metamagic costs are already being broken with that many metamagic add-ons, so why not go for the straight jacket when one's already visiting the mental hospital (as it were)?
Pretty simple without even going to Dragon Mag, Flaws, etc. Assuming I did the maths right.
Dragonblood Race
01Sorc Extend Spell
02Sorc
03Sorc Empower Spell
04Sorc
05Sorc
06Sorc Iron Will
07Incant
08Incant
09Incant Metamagic School Focus (Conjuration), B: Persist Spell
10Incant
11Incant
12Incant Maximize Spell, B:Repeat Spell
13Incant
14Incant
15Incant Practical Metamagic (Twin Spell), B:Twin Spell
16Incant
17Arcane
18Arcane Arcane Thesis (Abyssal Army)
Extend +1 (-1 Incant)
Empower +2 (-1 Incant, -1 AT)
Repeat +3 (-1 Incant, -1 AT, -1 MSF)
Maximize +3 (-1 Incant, -1 AT, -1 MSF)
Twin +4 (-1 Incant, -1 AT, -1 MSF, -1 PM)
And sure, Metamagic Effect Persist it, if it's a legal target.