While Akos doesn't hear anything he definitely sees the creatures coming. Two Huge monstrous spiders rise up out of the tall grass to the south of the road. Another two spiders of the same size try to clandestinely crawl up from the chasm, but the vermin are so big that they can't move very stealthily. Akso also sees another even larger spider crawling up on a rocky pillar jutting up near the middle of the chasm. It is Gargantuan in size.
Feel free to modify your post and definitely roll for initiative. I will wait for the others to make their rolls before having the NPCs respond to he appearance of the spiders.