Tohu takes the appearance of a three-faced young woman. She has two torsos and four arms (ending in long, clawed hands) but only one pair of legs. Her whole body except for the faces is made out of what appears to be coloured hair, growing from her three heads and woven into ribbons and cords.
Her faces and hands adopt the costume of the three capes she copies, twisted to fit her appearance. Her "hair" also changes to match the colour scheme of the head it grows from, resulting in flesh streaked and intermingled with the colours of the costumes.
She is the smallest Endbringer by height and size, with the possible exception of Bohu when not engorged.
In addition to the standard Endbringer durability, Tohu takes the powers and visages of up to three capes.
Tohu can mimic up to three capes at a time and then have access to all of their abilities. She can even adopt the powers of dead parahumans and parahumans who are half-way around the world. It's possible that she could even copy the powers of non-parahuman "capes". She seems to manifest her copied powers using the body parts that are copied from the original (e.g. shooting lasers using the hand mimicking Legend.)
It takes time for her to choose her "masks"; once she has chosen all three, the battle is essentially over. Weaver speculated that this time limit served as a counter to Scion, who often arrived too late.
Presumably, Tohu is not using the full extent of the powers under her possession, similarly to the other Endbringers.
Tohu first attacked alongside Bohu on October 10th, 2012. The attack was on the city of Bucharest, and Tohu selected parahumans that granted her massive air superiority, including powerful local aerokinetic Kazikli Bey. The defending forces didn't know how to combat the Twins, and the battle was considered a loss for humanity.
The Twins' second attack was on the Santa Fe Springs region of Los Angeles. The defending forces grasped that the key was to defeat them quickly before they ramped up; Tohu did in fact attain all three masks, but only part of the city was rendered uninhabitable by Bohu, and casualties were much lower than the previous attack. This was considered a victory attributed to Eidolon and the Guild.
Like the other Endbringers, Tohu fought alongside humanity on Gold Morning.
She helped to defend Earth Dalet from Scion alongside her sister and the defending forces.
At a key moment during the battle between Khepri and Scion, Tohu attacked Scion alongside the other Endbringers, wielding Glaistig Uaine, Eidolon and Myrddin's powers. The Endbringers continued to fight Scion as he was confronted with a false image of Eden and as Doormaker's power went dry. Despite Tohu's attempts to aid him, Leviathan was killed. After some more fighting, Tohu and the other Endbringers retreated, too injured to fight (with the partial exception of the Simurgh.)
Following Scion's defeat, the Endbringers went dormant.>
↑ 1.01.11.21.31.4Tohu, who would have been almost imperceptible if it weren't for the glow around her. Tohu, with three faces. Legend's white and blue mask, Eidolon's glowing shroud, and Kazikli Bey's red helmet, each twisted to be feminine, framed by the long hair that wove and wound together to form her body. It condensed into cords and ribbons, and the ribbons and cords, in turn, condensed into her chest and lower body, two torsos made with overlapping versions of the hairstuff, small breasted, with only one pair of legs at the lower half. The colors were extensions of the costumes she was copying, predominantly white here, but with streaks of crimson, green and sky blue highlighting the ridges and edges. Her four hands were long-fingered, claw-tipped extremities in shapes that served as mockeries of the people she was mimicking. Two of Eidolon's hands with the blue-green glow around them were holding a forcefield up to protect her sister, while a white-gloved one focused on using Legend's lasers to target capes who thought flying up and out of the city was a good idea. Not that it was easy to fly in winds like this. Not the sorts of winds that an aerokinetic like Kazikli Bey could make, capable of slicing someone with air compressed into razorlike ribbons. A hand in a red gauntlet was gesturing, redirecting the wind to blow down, across, and in crosswise currents that formed brief-lived whirlwinds. - Scarab 25.6
↑ 2.02.12.2Scion was killing the serpent-Endbringer… Leviathan. The smallest Endbringer, flying in the air, unloaded a laser, three of its shadow pets' attacks and two more ranged powers on the golden man. The resulting blast sent the ruined fragments of the settlement and the remains of the surrounding terrain spraying into the air. The resulting crater that compared with the one Leviathan had made in the real Brockton Bay. The blast had separated the two, leaving Leviathan hunched over, one arm intact and braced against the ground, head hanging, his chest peeled open. [...] In the moment he returned to an upright position, he flung out a sphere of golden light. The light curved in the air, and punched into Leviathan's open chest cavity. The Endbringer fell. The color went out of Leviathan, his flesh breaking up, like clay overbaked in a kiln. - Speck 30.6
↑ 3.03.13.2The Simurgh plunged from the clouds, hitting Scion. Leviathan, healed a touch, emerged from the water. Bohu rose from the earth, going from a human sized head and shoulders at eye level to a tower. Tohu, for her part, had Glaistig Uaine, Eidolon and Myrddin's faces. The Endbringers, come to the rescue. [...] Scion tried to float down to it, fighting almost tooth and nail with the Endbringers to get to his new companion. - Speck 30.5
↑ 4.04.1Tohu is really a threat [to the Justice League], if she can copy the Flash, Green Lantern and Martian Manhunter simultaneously. If you rule that she can only copy Wormverse capes, then she's just a very scary supervillain with an endless array of powers (due to copying people with access to hundreds or thousands of powers). [...] Tohu is one part of the Tohu-Bohu pair. She simulates powers, up to three individuals at time. She's small, but has the same overall toughness as the others. She defends Bohu. - Wildbow on Reddit
↑ 5.05.15.25.35.4Bucharest, October 10th, 2012 // Tohu Bohu Notes: First appearance. Loss. Tohu selects Legend, Eidolon, Kazikli Bey. Target/Consequence: see file Kazikli Bey. [...] Los Angeles, May 17th, 2013 // Tohu Bohu Notes: Victory by Eidolon/The Guild. Tohu selects Alexandria, Phir Sē, Lung. Target/Consequence: unknown. - Scarab 25.6
↑Another counter to Scion. All too often, he was late to arrive, and once Tohu had chosen three faces and Bohu had claimed the battlefield, well, the fight was more or less over. - Scarab 25.6
↑ 7.07.17.2They'd figured out how to fight Tohu and Bohu during the Los Angeles attack. The trick was responding quickly, stopping them before Tohu had her masks and Bohu managed her influence. They'd won, for lack of a better term, managing the fight without the casualties they'd seen in the prior attack, but they'd still lost a chunk of the city in the time it took them to beat and batter the towering Bohu into submission. Now Santa Fe Springs and all of the neighboring districts were uninhabitable, due to the traps that riddled it, the way the infrastructure had been completely and totally compromised. - Interlude 26a
↑Things weren't much different from before. The defense took a different form, they had Bohu and Tohu with them, and they were reshaping defenses to buy the defenders a little slack. But Dalet had taken heavy losses in an initial attack. - Venom 29.9
↑I could sense the doorways closing. Only the ones close to me remained open. [...] Scion was still engaged with the Endbringers in Gimel. We had seconds, a minute or two if we were lucky, to catch our breath, to think, plan and communicate. - Speck 30.6
↑He turned his attention to the winged Endbringer and her smaller companion. The towering Endbringer was already so damaged that she could only pull herself together. The fat Endbringer was gone. No, he was alive. He'd created a time field around himself, and was healing in a more distant location. Scion was doing too much damage to them. They wouldn't win this fight for us. [...] The giant monsters are losing to Scion, I thought. He's coming, soon. [...] In the other Earth, the winged Endbringer fell from high above, her innumerable wings broken, ruined and bent. She reached skyward, as if clutching for Scion, high above, and then the hand crumbled. The rest of her followed suit. The others were too broken to fight. S-ssionns c-comminng. [...] The moment he left Earth Gimel, the Simurgh scattered the mixed sand and dirt she'd gathered above her, then climbed to her feet, gun in hand. The pieces of the fake body she'd formed of the materials at hand broke apart as they fell free. She waited, recuperating. - Speck 30.6
↑I could see the Endbringer arrive. I'd opened a portal to Gimel in the process of making mouseholes between worlds, and she was the only one that remained. She sang, a shrill song that echoed in every mind I controlled - Speck 30.6
↑The Endbringers are, we're praying, dormant. The major players are busy recovering and rebuilding, giving us six straight months of peace for the first time in twenty years. - Teneral e.1
↑One window showed the various Endbringers, all of them motionless, but for the Simurgh, who was airborne. - Interlude: End
↑“Things are better this time,” Sveta said. “We’ve learned from mistakes. It’s a fresh start. The Endbringers are dormant, we’re finally building things without them being torn down all the time.” - Flare 2.6