Man From Mundania by Piers Anthony

You can move along pretty well
    when you get the hang of it. If you lose your balance, you
    just lock your legs around the log. You can't fall, really,
    if you keep your head." He sat down and demonstrated,
    awkwardly, on the flat surface.
     
    "How clever!" Ivy exclaimed, delighted. "Let's go!"
    Grey led the way again. This wasn't because he was
    brave, but because he just couldn't see making Ivy take a
    risk he wouldn't take himself. He pretended it was routine,
    but the truth was he was tight with fear. His hands were
    sweating, and his jaw was clenched; he hoped it didn't show.
     
    He walked as far as he dared, because that was the most
    efficient way to travel. Then he got down on hands and
    knees. When the arch became too narrow for that, he put
    his legs down and straddled the stone. He put his hands
    behind and heaved, humping his body forward.
     
    It worked. He kept doing it until the bridge peaked,
    descended, and widened. He tried not to look down, be-
    cause that made him unpleasantly dizzy; there was nothing
    down there except cruel stone, far below.
     
    When the stone became too wide he leaned forward
    until he lay on it, then lifted his legs, got to hands and
    knees, and moved on. It wasn't fan on the downslope, but
     
    it was a relief to be there.
     
    At last he reached the solid mountain again, and turned.
    There was Ivy, not far behind him. She was not as nervous
    about falling as he, because of her belief in magic, but he
     
    remained nervous about her.
     
    "That was fan," she exclaimed as she caught up to
    him. But some of the green of her hair seemed to be on
    her face, and he knew she had felt almost as queasy as he.
    This climb was certainly a challenge!
     
    They walked on up the path. The mountain was com-
    paratively slender here, but high, and the ledge was
    smaller. They had to go single file. This time Ivy took the
     
    Arlan front ArHJndanja            71
     
    lead, because he wanted to be in position to catch her if
    she slipped and started to fall. The path was increasingly
    steep, without steps, and still lacked any kind of guardrail;
     
    he would have been happier crawling up it, but that would
    have been too slow. Night was closing in.
     
    Then out of the gloomy sky came figures in the air.
    "Oopsy!" Ivy said, spying them. "Wyvems! Probably
    they forage here, picking off helpless climbers."
     
    "Such as us?" Grey asked, trying to suppress dread.
    He knew what wyverns were: small winged, fire-breathing
    dragons. Of course he didn't believe in them—but cer-
    tainly there was something ugly in the air, and that was
    apt to be just as bad for them as a fantasy creature.
     
    "Yes. But don't worry; I'll use my talent to foil them."
     
    "But your talent's Enhancement! Won't that just make
    them even more formidable?" Again, he was trying to
    make her see reason without actually expressing his dis-
    belief in her magic. At some point they would have to
    have this out—but not way up here on this treacherously
    exposed path!
     
    "Not necessarily. I'll show you."
     
    The flying figures loomed close—and they did indeed
    look like dragons. But of course such things could be
    mocked up and even be made to fly. This was obviously
    a most intricately fashioned setting, so such threats were
    feasible. Certainly those creatures, whatever their true na-
    ture, could be dangerous. He didn't see how enhancing
    them could help foil them, assuming it could be done at
    all.
     
    Ivy stood facing the dragons. She seemed to be concen-
    trating. The dragons approached even faster than before,
    their beady eyes glinting, plumes of smoke trailing from
    their nostrils.
     
    The lead dragon oriented and accelerated, flying di-
    rectly toward them. It jetted a column of fire. Grey started
    to scramble away, not wanting to get fried—but Ivy didn't
    move, and he couldn't leave her behind. So he forced him-
    self to wait, hoping that she did know what she was doing.
     
    The jet of fire missed.