I have an encounter in mind where the player characters come to a room that is 120 feet long, 45 feet wide and and 30 feet from ceiling to floor. The bottom 15 feet of the whole length of the room is cloaked in a permanent deeper darkness. The entry and exit to the room open up 15 feet over the floor just above the darkness. A stone pathway has been constructed at that level that spans the whole length from entry way to exit which rests on stone pillars (which are not visible thanks to the darkness). Three 10 foot sections of the pathway are missing but wooden planks have been placed over them allowing passage. The last 10 feet are a permanent silent image that looks like the last 10 feet of the bridge is whole (but actually never existed).
The original creators of the room intended it as a sort of extended pit trap but the trapped lengths have long since been triggered. The floor of the entire bottom of the chamber was lined in spikes but an unusually intelligent ogre has discovered the complex and cleared a path through the spikes all along the length of the pathway so he can use it to create ambushes. He has a way of seeing in the darkness and hides in the pit. After the characters have committed to the pathway (unless they figure out a better way to get across)he will (quietly as possible) remove the first 10 foot stone of the pathway behind them. If they don't see his hands reaching up out of the dark to do this then he will move to the last wooden plank, wait for a couple characters to get on and yank the planks out from under them. With the party separated he will work on the blinded and injured ones on the bottom and then worry about the rest.
I'm not totally evil...the players have a magic item they got at level one that will cast a daylight spell 1/day. If they remember they have it (they will be level 4-5 when this encounter happens) they can use it to dispel the darkness.
My problem is that the only way I figure out a way to give the ogre a way to see in the deeper darkness is to say give him a magic item that grants the effects of the Echolocation spell but only in that one room. I would rather figure out a way to give him blindsight or some other method of seeing in the pit but I can't think of way how without making him to high level for the encounter.
Any one have any ideas?
Well you could go the easy way and make it a Circlet of Mindsight that only works for Ogres.
Or just have him be a custom monster, an Ogre that developed blindsight (maybe he was born blind, next to radioactive magic waste or something).
If it works for your story, you might be able to build him as an Ogrekin with the Giant Creature simple template instead.
Ogrekin have two deformities each, see, which gives you room for customization. Simply give the ogrekin permanent blindness as his disadvantageous deformity, and blindsight as the advantageous deformity. If you keep the blingsight within a relatively short radius (like 15 to 30 ft. your players might even manage to be clever by staying back and attacking from afar.
To be around the same challenge as an actual Ogre, try taking the standard Human Ogrekin Fighter 2 (from page 204 of Bestiary 2), replace its Oversized Maw and Weak Mind deformities with blindness and blindsight, and apply the giant creature template to it. You'll get a large sized CR 3 melee fighter that should be similar enough to an ogre to fit your needs.
Gluttony, I bow to your Pathfinder Fu and hereby refer to you as Sensei Gluttony. Thanks!
I appreciate your suggestions too Rynjin!