Matau had wandered behind some rocks.  Krekka smiled and charged, already imagining how the Toa would beg for mercy. But when he reached the boulders, it wasn't Matau who was waiting there, but Krekka's partner.
"Nidhiki?" Krekka asked mystified.  "where'd the Toa go?"
"You must've let him slip past," snapped the other Dark Hunter. "Circle the other way back."
Krekka turned and left.  HE couldn't for the life of him figure out how Matua could have gone behind those rocks and then disappeared.  He would have been even more puzzled if he had looked over his shoulder and seen a second Nidhiki approaching in the distance.
When that Nidhiki reached the rocks, it was to see what appeared to be Krekka standing around doing nothing. "Where is the Toa?" Nidhiki demanded.
Krekka shrugged.
"You let him get by you?"
"Maybe he got by you" rumbled Krekka.
Nidhiki turned away, muttering something about Dark Hunters who weren't bright enough to come in out of a rockslide.  Once he was gone the "Krekka" he had been speaking to morphed into Matau, his mask glowing with Toa power.
"Shapeshifting!" said the Toa of Air. "Some mask powers are worth waiting for!"

Legends of Metru Nui, Greg Farshtey, p80-81