First, the idea that being separated from the Clot Cutter is inherently stupid, because we dropped it earlier to no ill effect.
Now, then. The theory I have is that messing with the game to gain more HP than our max caused a 10-turn-delayed effect that caused us to cough blood. There are three problems that need to be addressed for this theory to work:
1. Why did the surplus of HP cause a negative effect?
2. Why was it delayed?
3. Why was the negative effect limited to a moment of pain and a bit of blood?
I will address these one by one.
Issue I: Why did the surplus of HP cause a negative effect?
To answer this question, we need to consider what, exactly, a hit point is. It decreases when we are struck, and increases when we drink health potions. Most notably, though, having low HP has no negative or even cosmetic effects. Ciro has been walking around with 1 HP for a while, with not so much as a wheese, limp, or scratch. Clearly, hit points can't track "injuries," because no one in the Warrens is ever injured (well, almost no one). Despite this, however, running out of HP results in death. Moreover, you can increase your HP total! It's easy to see that hit points aren't simple.
Here's my thought. HP are not
hit points but
healing points. Everything in the Warrens has a theoretically fragile constitution--proven by this:
You can't just rip a person in half like that, not in the real world, and if you did they wouldn't explode like that. This suggests that the Warrensverse creatures aren't very tough. Instead, they can simply regenerate most wounds instantly. However, what allows them to do so? Look at the above image and note the color of the stuff spurting uniformly out of the halves of Al. What is it? Red, a bright red--much brighter than blood for the most part. What else is bright red? Healing potions. Thus, it seems that Warrensverse creatures produce a natural healing potion with which their wounds are automatically healed. This also explains how healing potions work--they replenish this supply--and why they can't heal past a certain point--you can't typically just stuff more and more liquid into a bag. As to why you die when you run out of HP, there are three possibilities: EITHER when you run out of Healing Points, your body can't keep up with its wounds and gives up; OR the HP stuff performs vital functions besides healing; OR you're actually out of HP stuff at HP=1.
Now, before I explain why going past our HP limit would be bad, there are two more considerations about HP: Purchasing MaxHP and Bloodshape. The latter, especially, seems to be pointing towards HP =~= Blood. However, these can be more easily explained with Healing Points than Hit Points.
Firstly, consider the shops. If HP are Hit Points or Health Points, how do you make someone more healthy or more able to resist hits? You can't, not really. HOWEVER, if they are Healing Points, it's possible to see some ways to change it. Presumably, there is some ingredient in the red liquid that is the "active ingredient" (herein referred to as the Healing Compound or HC) and some that are not (this will be returned to when we consider a couple possible reasons that excess HP would hurt someone). Obviously, if you want to hold more salt in a bag full of salt water, you have two options: Increase the size of the bag while keeping salinity constant, or increase the water's salinity. Presumably, buying HP alters your metabolism in such a way that you can create and/or tolerate higher concentrations of HC than you could otherwise.
Now, Bloodshape. It sounds like it rips blood out of your body and turns it into stuff, but there are two major difficulties with this idea: It takes
MHP (or MSP) rather than HP (or SP), and some weapons require MSP instead or in addition to MHP. To explain my criticisms, first consider this: Giving blood. If a person gives blood, they can simply recover--they're not permanently weaker until they can get a blood transfusion. Similarly, a mage who casts a spell can simply rest or something to regain SP--s/he doesn't permanently lose magical potency. So why does Bloodshape permanently weaken you? And, for that matter, if it takes blood, why do weapons sometimes require MSP as well? I'll address the point of taking MSP first, because it's simpler. Most if not all MSP-requiring items are projectile weapons of some kind, which generate their own ammunition/power/etc. Given their violation of conservation of mass and that they require magical energy, one can only assume that you're enchanting the item. Presumably, other enchantments would cost MSP, both to give a constant stream of magical energy and to keep enchanting things from becoming game breakers. Now, for the MHP thing. If Bloodshape did, indeed, rip your blood out of your body and turn it into something you'd expect it to cost HP, like any other kind of damaging effect; when Ciro gets a cut and bleeds, does she lose MHP? No! Hence, Bloodshape is clearly more than that. In this Healing Point theory, Bloodshape actually takes a mixture of blood, perhaps some HC, and some kind of stuff that determines the maximum HC concentration (along with mana-stuff if needed) and turns
that into the item. Such an art would require great concentration just to get the right mix, let alone shape it into something. This also explains why we can't Bloodshape from others' blood and why Bloodshaping has such common and painful failures--not only is great concentration required, if you screw up and draw, say, too much blood and not enough HC-concentration-regulating stuff (which I will now abbreviate to HCC) you will cause damage to yourself AND not have the proper mix to make a solid item. Incidentally, this mix explains why blood is able to be harder and more permanent than actual coagulated blood could be.
As a last consideration: Vampires draining blood to heal themselves makes a lot more sense if the "blood" is laced with natural healing potion. Either vampires can process it without toxicity or HC breaks down with normal creatures' digestive enzymes (presumably to avoid HC poisoning--see below).
Now that we've discovered the nature of HP (maybe), we need to consider the original question: Why would this be bad? There are two possibilities for why an excess amount of HC solution would be bad. Remember my above comment about increasing the salt in a bag of salt water? The first possibility is that the solution is simply more compressed, due to trying to squeeze more fluid into the same bag; however, not only would this cause immediate and severe problems, it's a bit crude and silly. Instead, it seems to me that HC is probably a bit toxic. Pretty much everything (even things that are healthful or even vital for life, like medicines and even water) is toxic in the right concentrations for some reason or another; presumably HC is no different. However, different people, even of the same size, even the same person at different times, can have different MHP. Why is this? There are three possibilities--higher HC tolerance, being able to turn HC into a less-toxic but equally-healing compound (inspired by the ability of certain tetrapods, such as many archosaurs, to turn urea into uric acid, and the ability of
most tetrapods to turn ammonia into urea), or the presence of substances which prevent HC poisoning. It doesn't matter much which is correct, but I'm leaning towards the last due to the presumed ability of Bloodshape to take such a substance and make it part of the "blood" and because it would be the easiest for a shopkeeper to increase. In any case, if you had more HC concentrated in your body than was safe, obviously that would be bad...though what KIND of bad varies.
Issue II: Why was it delayed?This one may be answered more briefly.
Very few toxins have instant effects. Alcohol takes a bit of time to take effect, water toxicity isn't obvious until it's far too late. While there are poisons which have near-instant effects, they are in a minority and are mostly chemicals intended to be poisons. Hence, there is no reason to believe that HC poisoning would be instantaneous.
Issue III: Why was the negative effect limited to a moment of pain and a bit of blood?I suspect that spitting up blood is analogous to fever of alcohol-induced vomiting--it's not an effect of the toxin, but rather a way the body defends itself against the dis-ease. Notably, the stuff seems to be about the same color as a healing potion, suggesting that the stuff being spat up includes a fair concentration of HC rather than simply being blood. If this theory is the truth, perhaps the pain was the body was either the first symptom of HC poisoning, or a side effect of Ciro's body shifting HC into her mouth or throat. Of course, since her HC levels were already below the safe maximum, there wasn't much to eject; presumably just HC that had already reacted to something inside Ciro. This is reflected in how Ciro takes not a single point of damage.