It's not a third season. It's an interesting but non-essential OVA series, set after the first two seasons but before Queen's Blade: Rebellion. It's telling us what happened next to everyone and in some cases exploring their characterisation more deeply, which I enjoyed. However it's also another BOOBS opportunity to show more of the BOOBS characterisation of BOOBS the regular cast BOOBS. (While showing lots of naked boobs.) The closing title sequences in particular live up/down to all prior sleaze standards.
In other words, it's Queen's Blade. If you liked the first two series, you'll like this too.
1. FAITH: ELINA'S UNSHAKABLE BOND
That was surprisingly dark. Gainos and Castle Vance are in new hands, but the nobles aren't happy about this and have raised an army to overthrow the queen. Elina leaps thoughtlessly into the fray, bragging that she could handle 500 soldiers on her own... and it's possible that she could have, but the nobles also hired Echidna.
Most of the episode is a conversation between Elina (crucified) and Echidna (amused). Elina's absolutely convinced that Leina will come and rescue her. She doesn't waver in her faith, no matter how long she waits and no matter how often Echidna tests her with inconvenient facts.
If Leina doesn't arrive in time, incidentally, then Elina will be executed.
This is unexpected depth in a character who'd always previously just been a source of incest gags and stomach-turning snobbery towards anyone not related to her by blood. (Might the latter even be a factor in the former?) Surprisingly, this works. I hadn't realised Elina had it in her. Eventually the episode's heartwarming, but the road there is rocky.
2. LONGING: ALLEYNE'S THOUSAND YEAR SEPARATION
It's a Nowa episode, which means it's lighter and happier than ep.1... until Nyx shows up.
Nowa is the nicest, most likeable character in Queen's Blade. Nyx though is a grovelling human wreck so devoid of confidence that she thinks being possessed by an evil tentacle rape demon is the only good thing in her life. (Seriously, her preparation for combat is to perform fellatio on Funikura, complete with a gushing white ejaculation. This is particularly blatant here.) Nyx also has two personalities, one timid and one angrily vengeful. She can also be funny, but it's dark comedy.
3. MELANCHOLY: AIRI'S DOUBLE-CROSS
It's a Melona-Airi episode, making it very obvious that the Swamp Witch they serve is the Devil in Hell. (If you're her servant, don't annoy her.) However Airi's not in the swamp at the moment. Instead she's with Rana. Is she going to choose good or evil?
For me, that made this the most gripping and emotional of these six episodes. Airi's sincerely devoted to the Swamp Witch, i.e. to serving evil. However her relationship with Rana is of a similar strength.
The episode's second half brings in Melpha and Nanael. Hilariously, Melpha's "holy poses" work. Flashing her whatsit is the divine equivalent of a U.S. air strike, although that might also be because she appears to be a better, holier person than Heaven itself. (Nanael on her own would significantly drag down the average level of virtue of the entire heavenly host.)
4. REVIVAL: MENACE'S PALACE OF PLEASURE
Melona and Airi go to drag the third member of their trio back to Hell, only to discover that Menace has rebuilt her lost kingdom of Amara in the desert. It's like ancient Egypt, obviously. This had always been Menace's goal, so she's not even remotely interested in going back to serve the Swamp Witch.
Apart from anything else, her current lifestyle includes drinking wine off her servants' naked boobs. Melona thinks this looks fun and turns turncoat, to Airi's disgust (but to no one's surprise). This isn't an episode of significant emotional depth, but the S&M was funny.
5. FALLEN ANGEL: THE NANAEL OF PLEASURE
Nanael pushes her luck too far and at last gets banished to the underworld. (Inevitable, surely?) There she meets Melona and Airi, whereupon the universe learns that Nanael was an even worse angel than we'd previously assumed. I reckon the episode's ending isn't what we're told, but instead is Heaven desperately backpedalling from the worst mistake they ever made.
Melpha is still holier than Heaven. However she's never stopped believing in Nanael, so she's also an idiot.
6. MYSTERY: AN ESCORT'S JOURNEY OF DISASTER
The weakest of these six episodes, alas, although it's still okay. That's a shame, because Tomoe's great. However her surprising travelling companion here has always been a fairly opaque character and that doesn't really change here. Even Shizuka's scenes aren't as emotional as I think they should have been.
These episodes are often pretty good, but they're also a bunch of fill-ins and epilogues. It's not really going anywhere. However the nudity is rampant, while the character work can be surprising. It's proudly and shamelessly maintaining the standards of Queen's Blade. (I carefully didn't say "keeping up".)