Meleoron's basic ability was the camouflage he possessed as a chameleon.
Although En or keen senses could detect this ability, his Nen Abilities, Perfect Plan and God's Accomplice, enhanced and improved upon his natural instincts.
They could be considered utterly overpowered Specialization Nen Abilities.
When Meleoron chose to hold his breath, he activated his Nen Ability, Perfect Plan. His presence would then be completely erased, making him undetectable through sight, hearing, smell, touch, Nen perception, or any other means.
God's Accomplice extended Perfect Plan to companions in contact with Meleoron.
Only one thing limited Meleoron's abilities: how long he could hold his breath.
While motionless, Meleoron could hold his breath for a maximum of two minutes. The greater the pressure, the shorter that time became. Under extreme pressure, he might lose his hold after just a few seconds.
Once everyone learned about Meleoron's abilities, they all understood just how overpowered they were.
Knov's eyes lit up. If Meleoron infiltrated the Palace with him, wouldn't that give him an even better chance of setting an exit somewhere safe and extremely close?
"Oh, right." Qiao Lun's attention turned to another issue. "Where's Killua?"
Gon had arrived, but Killua still hadn't. Could Killua have been ambushed by Chimera Ants and driven into a desperate situation after splitting up with Gon, just like in the manga?
Given Qiao Lun's presence, Killua probably still hadn't removed the needle from his brain. If he had been attacked, there was no telling how things would turn out.
"Sorry, I don't know. We split up." Gon looked worried too.
"It's all right." Although Qiao Lun was a little worried himself, with Killua's abilities, he should be able to pull through!
"Let me take a look." Palm took out a crystal ball held aloft by a shriveled mermaid corpse.