Couple of things:
My conjurer cannot summon anything that is not one step removed from Bane's LE alignment: LE, LN, NE only. No demons, just devils, daemons (yugoloths), nightmares, nighthags, formians, some LN celestials (protectors in Tome of Horroprs, for instance), etc. This is due to an irreversible choice I made in character development at 1st level (Theurgist "character concept" from Quintessential Wizard that gave me free arcane versions of all the planar ally spells and most of the summon monsters).
The only political stuff we've gotten to do so far:
Our group has made peaceful contact and formed a trade alliance with the drow of House Jaelre, so we should be able to unload drow only items to them for a profit. My conjurer has also forged an alliance with a Thayan merchant/slaver in Zhentil Keep who can provide all manner of exotic goods even the Zhentarim might have some difficulty coming up with on short notice. Unfortunately, they aren't willing to loan us more than three drow to help investigate Maerimydra. We used two fighter/rogues but they got their butts beat and so we let them go, especially when we realized we didn't necessarily need them and thery were draining our XP (we were close to levelling and wanted to make sure we did. I guess we could get two more and a mid-level leader type we've been dealing with to tag along.
Our group has forged an alliance with the 40+ wyverns of the Thunder Peaks (including their reasonably bright 20 HD leader). We provide them with livestock and a slave/farmer to tend the herds so they never run out of food and don't have to hunt. I also make liberal use of the mount spell to conjure up snacks for them (kind of like fast food as it it vanishes in their stomach some hours later). They call me "Maker of Horses", lol. So they loan us 10% of their flock (4 wyverns) as mounts/air support/beasts of burden in exchange for all this free food. However, we can't use the damn things underground. We've got several of the beasts charmed with charm monster just to make sure they stay friendly. With this alliance, we have complete air superiority in the Sessrendale region where our Zhentarim secret base is located (sssh! don't tell Elminster!).
We could easily convince some of the goody-two shoes Mistledale/Battledale folks we've made friendly with under guise of our cover identity as Sembian mercenaries looking for work, but the problem there is they would learn too much about our true natures and that could jeopardize our long range plans for the region if they got away. However, if we sent them in to do it for us...

Bane doesn't want the rod back, he wants it destroyed, so there's no reason we must go all the way. We could simply seal the do-gooders in with their instructions and then leave, monitoring their progress by scrying/sending spells.
We could also bring this matter of the necromancer and his rod to our superiors in the Keep, but they'd probably just assign us to deal with it, give us a few more people (probably to assassinate us at a key moment as we have many enemies jealous of our rapid rise to power), and then hog all the glory for pulling the mission off. I could perhaps swing it so they sent another group instead of us (how sweet that would be!), as Bane hasn't said "you and only you must do this for me;" we kind of stupidly volunteered out of religious obligation (sincerely wanting to do Bane's will), not realizing what we were getting ourselves into or how unbelievably eadly it was going to be. We can't be raised or resurrected or even wished back to life without Bane's consent and he doesn't tolerate failure very well, so we don't wanna die. Since all Bane needs is the mission completed by anybody, why should we do it if we can get someone else to do the job for us?