Permanent summons/constructs?

[heavyfuel]

Simple question.

Is it achievable in E6?

[Telonius]

Artificer can take Craft Construct as their 6th-level feat, so if they can otherwise meet the prerequisites they can craft any construct. (They can also make permanent Homunculi at 4th). Other classes could meet the prerequisites for the feat at levels 6+.

[J-H]

If you can get an Orange Ioun Stone to achieve CL7, you can use Beget Bogun.

Yes, it's a 1st-level Druid spell that requires CL7, a feat, a week of prep time, and 25xp.

[Inevitability]

A sorcerer or wizard 6 who uses their 6th-level feat on Extra Spell (Arcane Eye) can create a homunculus.

A familiar is also a permanent summon of some sort.

[Ruethgar]

There is a Construct Familiar feat as well as the Urban Druid ability to get an Animated Object Companion. Should be noted that the Animated Object can be released and retains its mobility in case you have Rebuke/Command Constructs.

[MaxiDuRaritry]

Psionic characters can have a psicrystal.

Also, Leadership and warforged.

[Zaq]

It's closer to a familiar or a companion than a summon, but I think you can just barely sneak into Master of Shadows (ToM pg. 121) and get a permanent Shadow Elemental. But that's probably not really what you wanted.

Basically anything else I can think of is either another variant on a familiar or is out of reach for people staying within the spirit of E6. If you allow Artificers to craft scrolls of 4th level spells (which I consider to be outside the spirit of E6, but I'm not your GM, so my opinion isn't the one that really matters), you can get things like Halaster's Fetch I (assuming you're okay with an Artificer using a Faerun spell) or Lesser Planar Ally, which kind of work?

The Sacrifice rules from BoVD can, assuming that your brand of E6 doesn't choke off any possibility of spells above 3rd level even existing at all, give you a Limited Wish or even a Wish (though you can only get the Wish once), which might let you get access to some helpful high-level spell (either one that can be used for a long-term summon or one that can help you meet some kind of prereq) if your GM is lenient, but I wouldn't be at all surprised if your GM wasn't too fond of that sort of thing.

[ShurikVch]

Create Crawling Claw is a 3rd level spell with Duration: Instantaneous

[Tvtyrant]

I personally use rituals for E6, and among them is Create Flesh Golem. You can also lesser planar bind a ravid for an army of gargantuan animated objects, although this requires artificer or sacrifices.

[MaxiDuRaritry]

A StP erudite psion with access to a psicrystal and alter self can turn his psicrystal into any construct with 5 HD or less up to Small size...like, say, an animated object.

Just one point in an E6 psicrystal's favor.

[Inevitability]

A 6th-level beguiler/warmage/dread necromancer with Versatile Spellcaster can take Extra Spell (Call Dretch Horde) to summon 2d4 dretches. Note that you can at most command 6 of these, though.

They're not exactly permanent, but they stick around for a year (two years with extend spell and metamagic reduction) and don't require expenditure of gold, XP or other resources beyond the single soul required to cast the spell.

[ATHATH]

I had a list of spells that created permanent or semi-permanent minions a while back. It might take me a while to find it again.

I'm pretty sure that there was a prestige class that got a spell that summoned 2d4 fiends for a year at a really low level. If you use a few feats to boost your skill cap high enough to get into Chameleon early enough, you can cast it.

Can we add Animate Dead to the pile?

[Extra Anchovies]

Can we add Animate Dead to the pile?

Yes indeed we can - the Death Master (DragComp) has it as a 2nd-level spell, so any 1st-level arcane caster can get it with Precocious Apprentice, and any spellcaster with 3rd-level spells can nab it via Extra Spell.

[Inevitability]

Yes indeed we can - the Death Master (DragComp) has it as a 2nd-level spell, so any 1st-level arcane caster can get it with Precocious Apprentice, and any spellcaster with 3rd-level spells can nab it via Extra Spell.

You could also be a bog-standard cleric and simply prepare the spell.