Lava Slugs
Looking at the simple key, Lin Mu found it a bit suspicious.
'A bit too simple…' Lin Mu thought as there were basically no Immortal Qi fluctuations coming from it at all.
This definitely would have made it hard to spot it even with their Immortal sense as the fire immortal Qi would cloud their senses. The simple key would have basically been a grain of sand in a sea; unassuming.
~shua~
Lin Mu made contact with the key with his Immortal sense and learned another thing about it.
"It really is a simple iron key." Lin Mu muttered.
"There must be something more to it." Lady Kang found it suspicious too.
~Ripple~
And sure enough, a few seconds later they felt the large lava lake in front of them ripple.
These ripples would have been easy to mistake for the normal ripples that happened due to the bubbling lava, but for the senses of two immortals, they easily stood out.