Yuan-ti.
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Under the direction of a hin named "Derek", a group of nine led by Grag headed off to investigate the rumours of yuan-ti. Some were simply willing to do their part, some could have been said to be in it for the treasure.
They travelled to the cave on the orc plains and came out nearly two days later, all intact.
Some might have overheard that they met a "war machine" or "tin man" out on the plains. Others might have heard that the yuan-ti have taken the temple within those caverns as their own.
