Diago is an ant girl who resides in the monster city Stonegate. There, she acts as a guardian over those who have been taken in, as well as an active fighter who accompanies their raiding parties on enemies in the nearby land.
Diago dresses in a short formfitting black skirt and sleeveless tunic that's ripped over her large breasts. She wears knee-high black boots, and dark gloves that have steel plating over the fingers, knuckles, and backhands. Her long dark brown hair matches the color of her eyes, her bug antennae sticks out over her messy locks, and her insect abdomen is colored black. She carries a large steel pickaxe with a chain strap to it and also has a coiled chain-link whip holstered on her hip.
In stark contrast to how most ant girls are, Diago is more a warrior than a digger. Hailing from a renowned and feared monster city, Diago proves her right of belonging there with her aggressive and often deadly fighting style. Despite being a fighter and quite intimidating, she has shown compassion to those in need and appears to house a benevolent soul behind her stoic and silent personality.
Unlike other ant girls in the series, Diago doesn't show much interest or activity when it comes to digging. The pickaxe she carries is used for combat rather than mining, and although she is often seen with dirt on her, her role in Stonegate is more of a fighter than a miner. She participates in raids against enemy factions, helps liberate humans who have been captured by more nefarious monsters, and in Stonegate acts as a watchman and general security for the citizens. She's also often seen taking direct orders from the countess, Eirene, to which she complies without hesitation.
When not on duty, Diago is known to spend most of her time watching over the children in Stonegate's orphanage within the underground sanctuary. It's even noted by Eirene that Diago spends so much of her time there she doesn't need to assign additional staff most of the time, knowing that Diago alone will always go above and beyond to take care of the children, both human and monster alike, as if she were their own mother. Depsite this comment usually getting a flustered scowl from Diago, she's never truly able to hide her true feelings and caring personality towards the children.
Another noticeable trait is that she never speaks, or squeaks, to anyone. Lucy has even made a comment about Diago being a "mute brute". This is because Diago is unable to speak, or even squeak in her own tongue, after she lost her voice from a witch's elixir.
In S2. Act III her backstory is brought to light. Before she lived in Stonegate, she was part of the Blacksands ant girl nest from the eastern region of Memgora, located in a desolate wasteland known as the Venderchenza Wastes. The black tunic ant girls are known to be very social creatures, with the majority of their nest resting on the service in the form of an expansive marketplace for a city. Diago was part of their collections team, also considered scavangers, as they scoured the wastelands for any merchandise they could sell. There were three human cities near their nest, however they were all filled with very strong and hardened humans, and as such the Blacksands could never steal any men for their queen, and instead had to rely on bartering for men with other monster communities.
After some time, men became so rare for them to acquire that they began to grow desperate. With no men being brought to their queen to keep their numbers up, the Blacksands were forced to use other methods to keep their colony alive. While Diago was away on a scavenging mission, the Blacksands turned to kidnapping little boys from the nearby cities and traveling convoys, seeing as those were the only humans that couldn't fight them off. With this they soon acquired all the breeding tools they wanted, as well as a new market for other monster races who wanted such young humans for their own needs. When Diago returned to her home, she was horrified to discover her nest had stooped to such lows in order to survive.
Despite her constant arguing and refusing to become like her fallen sisters, Diago soon became the only ant girl in her entire nest that opposed using little children for breeding. After keeping her resolve for so long, she was brought before her queen, and ridiculed by her ruler while all her sisters scoffed at her. Intending to break Diago's resolve, the queen had six boys brought into the chamber. With Diago held down by her sisters, the queen prepared to rape the boys right in front of her. However, this was as far as Diago could be pushed, and with the intent being made known to her, she finally snapped and blacked out in her rage. It was then Diago viciously attacked and murdered her sisters that attempted to hold her down, and then threatened her own queen. The boys witnessed Diago fighting off every ant girl that tried to stop her, with Diago murdering them all before finally killing her own queen by crushing her head with her bare hands.
Coming to her senses again, Diago freed the six boys and escorted them out of the city, fighting and killing every ant girl that tried to stop them along the way. During their escape a wagon filled with gremlin alchemic pouches that were being sold in the city was destroyed, causing a massive explosion to take out the city gates and separate Diago and the boys from the ant girls. However, one of the alchemic pouches infects Diago with a deadly poison before they make their escape.
After herding the boys away from the city into the wastelands, Diago succumbs to the poison in a cave. The boys, having witnessed her protecting them all this time, gather around her, urging her to get up and not leave them, even crying for her. Before Diago can die from the poison, a mysterious witch dressed as a bunny appears, having apparently seen Diago saving the boys from the lecherous ant girls, something she empathized with as she too hates the idea of harming children. Wishing to help, she offers the boys a strange elixir, claiming it should be able to cure Diago, however it is also an untested mixture. Wishing them luck, the witch departs, and after considering their options, the boys give Diago the elixir.
The following day Diago is shown to have made a full recovery, however its also revealed she lost her ability to speak. The boys plead for Diago to forgive them and that they only wanted to help her, with Diago being amazed at knowing they cared for her so much. With her strength restored, Diago leads them out of the wasteland, and eventually into Koskaysil.
One day the boys fall ill from a deadly fever, something Diago is unable to help them with. As luck would have it though, a convoy from Stonegate came across them along with Doc, who is able to cure the boys without any trouble. Seeing Diago is a kind and caring soul towards humans, Doc extends an invite for them to come to Stonegate, where they then all head towards to start a new life together.
The six children Diago saved from her nest have remained in her protective care ever since, and currently reside in Stonegate along with the ant girl who they all treat as their queen. In fact they go so far as to act as her personal guard, dressing up in makeshift armor they likely found in a junkyard, and wielding wooden swords all in the name of their revered ant girl. Although the orphans at Stonegate adore Diago for her kind and caring nature with them, Diago's Six appear to be completely devoted to serving their queen however they can, with the six boys always opting to stay by her side whenever able while warding away strangers with bold and overconfident talk and a show of their swords, however their actual combat abilities are severely lacking.
- Diago’s character was first designed to be that of a scavenger ant girl who leads a raid on Queen Victoria’s nest at the end of Act XII. She was originally planned to be a villain, with her killing Victoria before the book ended. This was scrapped as a different plan for Victoria and her nest was set by the author, and instead Diago was written as a hero who saves Kroanette in Act XII.