Kylearan's Tower  
 
The magic mouth at 10n/13e will teleport you to 8n/9e. The answer is 'Stone Golem'. 
The magic mouth at 2n/12e opens the magic door at 6n/1e. The answer is 'Sinister'. 
If you didn't get the crystal sword from Harkyn's, then go back for it or you will have to suicide to get out of Kylearan's. 
Kylearan will give you the onyx key. As usual, make sure your inventory isn't full. 
Grab the silver triangle (Electronic Art's logo piece two of three). See above about inventory. 
 
1 As a guardian He must walk... The first part of his name means rock. 
2 Made of earth
Yet without soul
As living statue
He is whole 
3 Beware the sting at the tail (south) of the Serpent-way. 
CG Crystal Golem 
M Magic Mouth 
S Stasis Chamber 
K Kylearan 
  Silver Triangle 
 
