I love all things Norse Mythology, I was also a big fan of the Valkyrie Profile games, first though I realize it's just a typo, I think it's spelled Einherjar. But that's a very minor thing. On to the meat!
Typo should be fixed now.
Valkyrie Body- It says they gain outsider traits, but doesn't actually seem to say if there is a type change. Maybe clear that up (Such as Outsider (Native)
Like the other non-template monster classes, there's no type change per se. Valkyrie is both the class and base race, and they're an outsider that's not native to the material plane.
The limitation on Chooser of the Slain, might make it difficult to see real-time play. That limitation being "Can collect freshly killed. Cannot collect any she or her allies killed. " this is obviously a campaign by campaign thing, but that might make it difficult for some Valkyries to ever fulfill their job. Maybe make it more difficult (Like a diplomacy check or something akin.) to turn someone you personally have slain, with a higher penalty for someone your allies have slain. (See it as a chance at Redemption.)
Well most D&D campaigns should have no lack of people kicking the bucket in violent ways, but I can see your point so added a custom feat to allow a Valkyrie to try to convert their own victims in Einherjars.
I'd also recommend making it so that they have a general knowledge of WHERE a person died. The way it reads, they can sense when a humanoid dies in combat, but it doesn't specify if they know the direction/location. While the Valkyrie does get Plan Shift at a later date, there is still no mention of knowing the location of a fallen/killed humanoid. Other then Sense, which is vague.
Ups, could've sworn I had added something along those lines but seems like I completely forgot to actually write it.
Now the Valkyrie knows the direction and distance of those killed in battle plus their HD.
Angel of Death- I actually quite like this, and it makes me want to add another option or two to the winged creature template, I'll give it thought.
Great, it was actually one of the first bits I added since I really love how Lenneth's wings transform.
Battle Maiden- I'd strongly recommend changing Longsword's bonus to a maximum of 15-20 (Doesn't stack with other forms of improving critical threat.) As if someone plays it right/well, and gets an abnormally high Cha, they'll basically threaten a critical strike on every attack, or nearly every attack. Since right now it doesn't call out that it doesn't stack.
Added anti-stacking clause. I think that should be enough, since the Valkyrie's still a bit MAD so she can't afford to only pump Cha plus it's still a just a longsword that must be held with both hands so even if you get a 10-20 crit threat it's still not exactly a dual lance ubercharger.
I personally think the chassis is super good. Maybe add a bit more of a buffer/supportive role though. Like a weaker or (comes online later) variant of Lay on Hands, but it only works on the Valkyrie or their einherjars. I feel like it'd be interesting to explore the possibilities of making it a battle field commander type, as that's usually how Lenneth was portrayed from what I remember of the first. I'll give it some more thought and see if I can come to a non-hamfisted way to do such.
I would say maneuvers can help cover that, in particular stuff like White Raven. Also I got a stronger impression of Lenneth being more of a frontline commander being closest to the enemy and being quite the hard hitter herself while being able to take hits herself. According to the wiki it seems like only in the sequel does she actually gets healing/support magic, but I know little about Valkyrie Profile 2.
Anyway suggestions welcome, I personally think the class is already quite packed between minions and maneuvers and one ability at every level but we can always do some ACF/feats to cover different angles.
No Honor Equal reads...in a very confusing way. Does this mean your Einherjars gain permanent spells even though you don't? So long as the person you sent was related to them by blood? Sorry I don't think I'm grasping how that's supposed to work well.
It's supposed to be two separate effects. The spell gained by sending an Einherjar is shared by the Valkyrie and her personal Einherjars, plus
you get the feather that grants a permanent buff but should only work for a non-Einherjar that is blood related to the Einherjar you sent to get the spell. Cleaned the text a bit, should be clearer now.
The way Divine Assault works, seems to require you to be running 3 Einherjars at least. As well as reading Sacred Phase, this means that a level 6th level Valkyrie has to have two level 1s, and a level 2 following the Valkyrie around. (6-2=4 Levels to split up between them.) Taking a level 1 into an ECL 6 encounter is tricky, and requiring all 3 of these companions to actively attack and damage the creature for Divine Assault to proc. (Unless I'm reading it wrong, as I said it doesn't seem to be worded super well.) I really, really like the concept though.
ECL (Effective Challenge Level) is not calculated as a simple sum. Two lv1s would have an ECL of 2, add in another level 2 and you get +2 ECL for ECL 4... Ok, I guess for low level it works like the sum. But a Valkyrie 10 could have ECL 8, meaning, say, two lv4 (ECl 6) plus a lv6 (ECL 6) would be ECL 8.
Of course you also need to take in account the Valkyrie grants multiple buffs to her Einherjars like Temper Steel, Sacred Phase, Angel of Death, No Honor Equal that'll make them fight above their apparent levels, plus the Valkyrie herself can be the one helping set up a Divine Assault for one of the Einherjars to deliver the buffed attack. And that's before taking in account another party member may be a group buffer themselves, throw in a Bard and those lv1s become a lot more dangerous.
Also added an extra buff to Chooser of the Slain that Einherjars can count their HD/level as the Valkyrie's own in order to resist effects like Blasphemy and whatnot.
All in all it seems like it'd be fun, but it'd be tricky to play in a party. I'd honestly be super excited to see some options for a Valkyrie to have party members as Einherjars. As I think that'd be a very fun RP thing to do. That's all I can think of for now, other then obviously a few missing abilities, and missing text. (Such as Valkyrie profile being empty.) It'd be super cool to see this get worked on, and I'll certainly read it again here and there to better understand it, as well as help you work on it.
Great idea about PCs as Einherjars, added a spoiler for that at the end of Chooser of the Slain. Basically they get to ignore the level limit and come back faster but count towards how many Einherjars the Valkyrie can keep out and must be kept summoned over other Einherjars.
And yes, more help to further polish this would be most welcome.
Also wrote down something for the 19th and 20th level abilities.