She is thrown back by the explosion and is seriously hurt, but it’s far better than dying!  Praise the Inheritor!  This is why demon lords are normally sensible enough not to enter the material plane in person!

She doesn’t have that many sixth circle slots to spare but she needs to be fully recovered quickly.  Heal

It is perhaps lucky for all involved that Tanya does not know her intervention is causing the locals to praise god.

Fire effective, target retreating. A bigger shot would take it out but would take too long to charge up and cause even more collateral damage. However, the target's barrier or its equivalent should now be down - she can't make sense of these signatures but if most of her shot hadn't been absorbed by some kind of shields, the result would have been much more impressive - so she can use enchanted rounds and land them on-target.

The advantage of enchanted rounds, besides their versatility, is that they can be fired as quickly as the gun cycles; the bullets and the orbs are both optimized to apply the standard enchantments very quickly. The standard-issue service firearm for aerial mages is a semi-automatic rifle; ace mages can enchant bullets as quickly as they can pull the trigger, that is, several times per second.

Tanya's preferred weapon is a SIG MKMS light submachine gun. It can fire fourteen rounds per second if you fully depress the trigger.

She snaps off a couple of AP rounds followed by a small explosive shot straight into the wound hole in the target, all in two-tenths of a second, to judge the effect.

His raw divine profane nature manages to deflect one of the armor piercing bullets, but another penetrates deeply, even with Deskari's sheer durability.  Its velocity remains even as Deskari's spell resistance negates its active enchantments.  The armor piercing round isn't Cold Iron or Good or innately Mythic, but it has enough kinetic energy to sting even so.  The explosive shot also connects, but it relies on magic activating after contact, and this magic is snuffed out, leaving an anemic explosion that doesn't even scratch Deskari.  Deskari would avoid flinching, but he wants to avoid letting his injured portions be damaged further, so a keen observer will be able to notice him shifting his body to protect the gaping wound in his chest and ready himself to try to dodge further projectiles.

Two tenths of a second is short enough that he's still not through the Gate yet.  He can mentally direct some swarms at where he thinks the latest attacks (extremely expensively enchanted sling bullets, slung at the rate of a hasted veteran adventurer?) came from.  A sling is an odd choice of weapon for a conventional spellcaster, perhaps she is some sling analog to a sword magus?  She better hope she can sling down swarms, haha!

It is deeply unfair that the locals can negate her magic while she can't make head nor tails of what's going on! At this rate the target will escape into the ?magical hole? and Tanya will be blamed for killing bystanders! She needs that thing to stay here and stand trial for - destroying that fortress, there must have been people inside, that is definitely a hostile and a legitimate target, but her bullets didn't do enough damage and the optical spell did but it wasn't quick enough -

Its ?head? is pretty large but its legs are very thin, can she cut through them with optical spells?

She can cut off two legs before it gets through the “hole”!  The demonic construct is somehow relatively unimpaired by the loss of legs.  (Probably some type of magical flight?)  The “hole” is still open if she want to dive and give chase?

She may not have noticed them earlier, but apparently locusts started swarming with the demon attack?  The earlier explosion killed and scattered a lot of them in the plaza itself, but locust swarms further from the blast survived and are gathering again.  Some are flying up in the air (towards Tanya’s location… a few seconds ago).  Some are going towards the legs.

He can continue to direct and sense through his swarms even through the Gate, so he will risk leaving it open another few rounds.  He will have his locusts consume his lost limbs so they can’t be used as spell foci or components against him.

The follow-up attacks are confusing, why would Iomedae bother on a merely annoying and humiliating follow-up?  She’s far too miserly and conservative with her limited power to do that… perhaps he assumed wrongly and the intervention was actually Calistria or some Chaotic God?

Actually… he’s already regenerating from the first devastating blow, which is evidence against a direct divine smiting, which would cripple his regeneration.  Perhaps a less divine intervention, overcharging the first attack, the follow-ups of which took his legs?

He can dig the bullet out of himself to study later.

Why are Deskari’s swarms converging on his legs?  …To stop her from obtaining the legs by eating them!  She’ll blast the swarms with a cone of cold.  

She still has several confusions (why the incomplete follow up on smiting Deskari, how did the demons overcome the Wardstone, …how could she have let this happen?).  But she’ll focus on the fight right in front of her for the moment.

She doesn't understand what Terendelev's construct is doing or why but presumably she knows best and Tanya shouldn't interfere. The insects aren't a concern on her current trajectory, she's climbing much faster than they are and still accelerating. It's a clear day and she can snipe everyone just fine from a mile up.

She could chase the target, it's obviously a loss to let it get away, but that's not a serious option. She doesn't understand the magical hole (?) and doesn't know what's waiting on the other side and isn't about to abandon the safety of the skies to blindly chase down scalps into melee range of an enormous magical construct. Terendelev can deal with it.

...she'll stay where she can see the hole, though, and snipe through it if she gets the chance.

What else is going on around here that she should do something about, were there more terrorist attacks in the rest of the city, is her airspace still empty, visual double-check to back up the radar and magic sensors...

In the city below, combat rages… aside from occasional bits of fire and lightening and ice and glowing weapons (almost all of which are discernible as magic to Tanya’s senses) the combat is clearly low tech: swords and spears and glaives and crossbow bolt.  The demons seem to have more magic than the humans (and human like species).  There is no one seriously approaching her altitude, demons and an occasional human fly, but at speeds comparable to birds (at most) and usually only to gain minor tactical advantages in ground engagements.

Down in the plaza she flew up from, Terendelev’s construct has grabbed both of the demonic construct’s legs, and it is yelling instructions to survivors (although Tanya can’t hear them from her altitude).  A child (or maybe short human-like species) grabs a fragment of the construct’s legs and runs off with it.  The ‘hole’ the demonic construct disappeared into disappears, although there is a more mundane rift left that reaches into caves below the city.

Some demon (one that looks quite classical to earth mythology if Tanya manages to spot: a small bipedal goat like creature) must have noticed her lower altitude decoy illusion, and manages to land a fireball on it.  The explosion of the fireball is a bit odd if you’re used to more physics-bound explosions, spreading from a point but cutting off sharply at 20 feet.