I make no claims to the Legend of Zelda.
Oasa had no need for tricks or deceptions to learn her target's identity. She simply walked among the people of Hyrule, probing their minds to find the right kind of memories. When she found such memories, she sank the hooks of her magic into them and ripped them out. Then she balled them up and swallowed them, digesting them at her leisure.
Each individual memory was only a little clue. A green-robed figure riding atop a little brown horse; a merry laugh just around the corner; a friendly face and a steady hand at a time of need. But by piecing such clues together, Oasa eventually worked out something like a complete picture. It was Link as others saw him; while questionable for philosophical matters, it fully sufficed for Oasa's simple purposes.
For the next step she snuck up behind a child and caught his shadow with her long, clawlike fingers. Before the little boy knew anything was happening, Oasa had stolen his shadow along with a measure of his vitality. And then she spread that shadow on the ground and pumped it full of people's memories of Link until it looked almost substantial. No longer flat, the shadow stood up and began a staggering walk. Oasa followed it at a little distance, knowing it would seek out the origin of the memories filling it.
The shadow found Link not far from the Royal Castle. Shortly thereafter it found oblivion as Link assumed one of his old enemies had returned. But it didn't matter. The Link-shadow was never meant to fight. Its only task was to follow the footsteps of the true Link, and to lead Oasa to him.
And once she found him, Oasa approached Link, moving as though her legs had been broken and reshaped and then healed time and again. And before he had time to so much as stare at her properly, she left her own body and dove inside his mind.
On the mental plane Oasa could properly be a spider. In this form she always felt more primal, more raw than when trapped within her body made of meat. So even though logic dictated that she should find the fastest way to kill the hero before his mind began to mount a defense, Oasa obeyed her instincts and ambled over to the boy's memories. She would kill him slowly, she decided. She would drain his memories, then his very self and finally crush the empty shell left behind.
She wrapped her legs around the first memory and bit into it, drinking…
… The wailing scream cut through her ears and mind. Her limbs froze and she could do nothing as the ReDead approached. For once in her life she felt what it was like to be helpless.
The undead creature wrapped its limbs around her body, its ashen skin feeling like coarse paper. Its rotted teeth scraped at her face. She felt pain and smelled death and she wanted nothing more than to run…
…away from the memory, as quickly as possible. Skittering and diving, Oasa ran. But in her running she failed to look ahead and stumbled into another of Link's memories. She spooked…
…at the sight of pale, ghostly hands emanating from the floor. The creature in the center of the room was after her and when it strangled her, she would die here among the horrors of the well. She knew that beyond this room were even worse ones. She needed to get…
…away from there and stumble into yet another memory to behold…
…the inside of a Like-Like's stomach, its digestive juices churning all about her as they settled over her face and clothes…
She kept thrashing, crashing into memory after memory, beholding ever new sights, each worse than the other.
…the grinding stone teeth of the Moon as it fell towards he world, as pained as it was unstoppable…
…the visage of a great boar-demon as it raised all the powers of evil just to kill her…
…the taste of poisoned swamp waters as they rushed into her mouth and her lungs…
Terrified and pained, Oasa ripped herself from the hero's mind. She knew it meant admitting failure – something she'd been terrified of all her life. But she knew now that there were far, far worse things to be terrified of. She tried to run and keep running forever, but she was weakened by the exertion and the horror. Her legs wouldn't move when she told them to.
She looked up to see that Link was preparing a spell of his own. It was less subtle than her magics, but it had the advantage of not exposing him to the mind of an enemy. Oasa closed her eyes a moment before the torrent of fire crashed into her. Her body, dry and dusty like a Gibdo's, burned quickly and nearly painlessly. But Oasa had just enough time left to learn to be afraid of fire.
When Oasa failed to return, Vehl and Erliol stared at each other with mixed feelings. Nevertheless, Vehl prepared to take his turn. Vehl the assassin who killed quickly and efficiently, without ceremony or pomp. He waited behind every door and under every bed, a shadow at midnight or just another peasant at noon. He would do whatever it took to reach and kill his target and enjoyed nothing so much as a job well done.
"I will show you how a professional operates," he promised Erliol.
And the two of them watched the sun set.