Complete Monster: Ra's al Ghul is imagined here as a stand-in for Abdul Alhazred, the Mad Arab. Having written the Testament of Ghul years back and been rent apart by an invisible beast afterward, Ra's is resurrected by his daughter Talia and immediately returns to business, drowning Gotham in a sea of reptiles and proclaiming Bruce Wayne their first victim. Now a faithful servant of the eldritch god Iog-Sotha, Ra's seeks to allow Iog-Sotha passage into the world to end all humanity and begins arranging the material for its arrival, tearing through the now-mad Grendon and leaving him to slowly freeze to death while sending a plant demon he creates from Grendon's seed to assassinate Oliver Queen and nearly murder the young Tim Drake. Afterward, Ra's has Harvey Dent subjected to a horrific, painful mutation that eventually renders Harvey immobile and twists half his body into a gate through which Ra's attempts to draw Iog-Sotha forth. Ra's mutates his own body in his final, furious attempt to slay Bruce, fanatically claiming that a "million million" souls will follow Bruce into Hell when Iog-Sotha makes its crossing.
Ra's al Ghul is a dark priest and a servant of an Outer God, Iog-Sotha. Uncovering the secrets of the ancient Serpents, Ra's desires to unleash Iog-Sotha upon the world, which would result in the planet's destruction. Spreading a horde of reptiles across Gotham, Ra's has the brainwashed Grendon killed, using his remains to create Poison Ivy, whom he uses to painfully mutate Harvey Dent into "The Door". Performing a ritual to release Iog-Sotha, Ra's turns into a monster to kill Bruce Wayne, before using his last strength to keep the portal open to ensure that Iog-Sotha will cross over to Earth and annihilate humanity.
Talia al Ghul is the last remaining member of the Cult of Ghul, who wants to help her father destroy the world. Killing Kirk Langstrom and leaving his corpse in Wayne Manor to manipulate Bruce Wayne to locate the Testament of Ghul for her, Talia also painfully murders Professor Munford by having a Djinn devour him from the inside. Sending Killer Croc to retrieve Grendon, which results in him brutally tearing apart Dick Grayson, Talia resurrects her father and assists him in his rituals, openly desiring to cause the end of humanity out of fanaticism.
Continuity Lockout: A fairly deep knowledge of the Batman (and to a lesser extent, Cthulhu) mythos is needed to understand many of the events of the story, since the only answer for "why is this happening?" is usually "it's a reference". No explanation at all is provided for who Etrigan is, despite this being fairly important to the resolution.
Unexpected Character: Cassandra Cain having Tim Drake's role from the comic, albeit with an Adaptation Name Change to "Kai Li Cain". In practice, her role is more of a Composite Character of both (plus Carrie Kelley), but the fact remains that both Tim and Cass tend to appear in DC animation much less often than other "regular" Robins or Batgirls ("regular" as opposed to Carrie, who is Robin in an alternate future). This is only Cass's second substantial animated appearance, after Young Justice (2010), and the third and briefest being a voiceless, costumeless Genius Bonus cameo together with Tim in Justice League.
