The stone ruins inside Navrey's lair can be used to activate a secret mechanism which drops a heavy pile of rocks on her. The rocks damage her by about 30% of her overall health.
The mechanism is activated by clicking three stone ruins found inside her lair. Each stone ruin has a little part which is clickable and will change its color for a certain duration of time. To drop the rocks all three ruins must by activated at the same time.
This can either be accomplished by having three characters (one at each stone ruin) or by one character running all three stone ruins.
When trying to activate the mechanism with only one character it is important to activate them in the right order. One stone will stay active for 9 seconds, one for 6 seconds and one for 3 seconds. It is possible to activate the 9 seconds stone, run to the 6 seconds stone and activate it, and then finally run to the 3 seconds stone and activate it.
The timers rotate among the three stone ruins randomly once a day. After activating it, the mechanism has a cooldown timer of about five minutes before it can be used again.