Meru and Dalia are natives of the planet Cherron, a world divided into two sects: "Meru's people, the Haifs, smug supercilious telepaths, philosophers, and scientists who could not be bothered with what they called mundane labors...and Dalia's people, the Haif-Nas, a noble people, subjugated and driven into slavery! It was inevitable that revolution fomented in that atmosphere of vile oppression!" (take a guess which one's version that was!). The Haif-Nas tried reason and diplomacy, but the Hais responded by tightening the yoke. The Haif-Nas demanded freedom and equality or Cherron would be destroyed. The Haifs scoffed at this threat, but the Haif-Nas destroyed key power stations across Cherron, setting up a chain reaction in the planet's core that tore it apart.
In spite of the stigma to each of them, Meru and Dalia had fallen in love. Perhaps following a suggestion of Dalia's, Meru took her to a world where they could share their love freely. Thus they were both off world when Cherron was destroyed, and each was the last survivor of his or her sect. Meru was furious that Dalia had known that this was coming, and Dalia fled from him. Meru tracked her for unknown ages. Eventually Dalia came to Earth, where she transformed into the form of "Jane Doe" and induced a hypnotic-trance to wipe her brain clean of all memory, as protection from Meru's probes.
"Jane Doe", a homeless woman living on the streets of Manhattan, was badly injured during a shoot-out between the police and some bank robbers. She was taken to Mount Sinai Hospital where her life was saved by Dr. Donald Blake. About that same time, Meru finally pierced the veil of Dalia's probes, and he came to Earth and attempted to attack her in mid-operation. Spider-Man attempted to stop Meru, but after taking one of his mind-blasts, Spidey didn't see any reason to stick his neck out for the public that hated him, and he took off. Spidey had delayed Meru enough to allow Blake to finish the operation, and he became Thor and overpowered Meru, who fled.
Meru next showed up in Times Square, blasting all the people there, and demanding (in an alien language...maybe he was using telepathy) that the city turn over Dalia to him. Meru's public actions made the news, and upon seeing him, "Jane" regained her memory. Thor again tackled Meru, but this time Meru used his power on Thor, putting Blake's mind in ascendance. Unused to fighting, or moving Thor's much larger frame, Blake was no match for Meru, who put the kibosh on him. Spidey was able to overcome his selfish emotions and swung to Thor's rescue, saving him from being thrown off a roof by Meru. Spidey tackled Meru, and ended up getting tossed off the roof himself, but again he gave Blake some extra time, which allowed him to collect himself. In the fury of battle, Thor's mind took control again, and he made short work of Meru. "Jane" suddenly appeared, revealed herself as Dalia and threw Meru off the roof (a lot of that going around this issue). Spidey saved Meru, who revived and attacked Dalia. As they chided each other for betrayal and what-not, Meru overloaded his blaster-weapon, which blew up and disintegrated them both.
Meru and Dalia's formless, intertwined essences floated through Manhattan, and they came to the agreement that they wanted revenge on Spider-Man and Thor, whom they blamed for their plight. They sensed the magical properties of the sword Dragonfang, entered it, and used its energies to take control of the Valkyrie. They then sent the Valkyrie on a rampage, hoping to attract the attention of their targets. Spidey showed up first, and attempted to subdue the bloodthirsty Valkyrie. Thor came along soon after, and mistaking the Valkyrie to be the victim, he swatted Spidey aside, but then had to defend himself from Val's sword. During the course of the battle, Spidey had noticed that Val seemed less battle-crazed when she parted with Dragonfang. He swung down and pulled it from Val's hands as she fought Thor, which cleared her mind, and left her and Thor to make googly-eyes at each other, as the possessed Sword pulled him into the air and across town. Spidey finally got their attention, and Thor shattered the sword, expelling the disembodied form of the merged aliens. Thor then made a warp in space and sent the energy form away.
Meru (and most likely Dalia, since they were last seen merged) was captured by the Stranger. He was returned to his original form, and imprisoned on the Stranger's laboratory world, where he underwent various forms of tests. During the Overmind's attack on the Stranger, Meru was one of those freed and sent to attack the Stranger's allies. Meru was one of several former prisoners being transported to the site of the struggle between the Overmind and the Stranger's forces. Dr. Spectrum (of the Squadron Supreme) was the transporter, but in mid-flight he regained his own mind, as the Overmind withdrew his influence to focus his full power against the Stranger. Spectrum then dropped Meru and the others, leaving them to fend for themselves. Many of the Stranger's former prisoners escaped after this struggle, but Meru's fate is unrevealed.
Powers and Abilities
Meru possessed superhuman strength and durability. He could fire a blast that would cause repressed feelings and emotions to come to the surface in his victim. This would often cause them to act selfishly, fearfully, etc. While merged with Dalia, he demonstrated the ability to enter and levitate inanimate objects. It was only the mystic properties of the sword Dragonfang that allowed them to control the Valkyrie.
His platform apparently amplified his mental powers, allowing him to affect large crowds of people at once.
Meru used a floating platform to fly through the air, and presumably had an interstellar ship as well.