#2:
Ability requirements: Phase.
At the first two vampires you come to (they are eating a human......YUK!, & you gotta move a block to proceed on) there should be a lake just in front of you, jump on in & phase through the gate.

#3:
Ability requirements: Phase.
In Raziel's clan territory just before his portal, just after you fight two vampires that jump from behind walls or pillars or whatever, there is a closed gate on your right & a movable pillar on the left, move the pillar to the gate, jump on top of the pillar, side step then phase through the gate.

#4:
Ability requirements: Phase.
When you enter the Sanctuary of the clans/ Pillars of Nosgoth/ Kain's first castle (you gotta phase through the far gate) a Pie/ Pizza piece will be right in front of you.

#5:
Ability requirements: Phase & Soul Reaver.
In the silenced cathedral (you need the Soul reaver to gain entry) after you manage to move the big block in the wall near the lower bell go left, left again & through the doors, you should now be near a little dome with a pie piece in it, Phase through a red gate nearby & solve the wall mural puzzle to open the dome.

#6:
Ability requirements: Phase.
Just after you kill Melciah and exit his lair a short Mini-Movie should have the elder god telling you that you can now go to places where before your progress was impeded. Now jump into the lake there & look around (don't worry about side stepping, you do that automatically when you go in water----until you learn to swim) see a gate with a pie piece behind it? (stand where you are & use L2 or/and R2) wel phase through it.

#7:
Ability requirements: Climb.
On that murky lake just before Melciah's lair where you gotta leap from island to island, look around for a climbable wall, then climb it!

#8:
Ability requirements: Projectile & Climb.
Go to that place with a big(BEEP)s skull, go in the eye socket, follow the path until you get to a Veranda/Patio overlooking everything, jump left to a torch lit ledge, then use L2 & R2 to aim the Projectile at a square block & hit it to push it onto a hole in the wall, jump down & look for a climbable wall, then climb it & ceep climbing & exploring for a pie piece.

#9:
Ability requirements: Climb.
In the Human Citadel between the bridge  with a woman on it over a lake & a big water holder/container.....thingy, go through the door on the left & explore until you find a little water-fall going along the floor, face the wall the water is falling from & climb up it.

#10:
Ability requirements: Phase.
In the Human Citadel past the big water container thing go through a few doors and there should be a lake that leads into a cave*, on the other side of this lake there is a wheel, turn it & the water should drain away, go into and follow the cave & jump down, kill the vampire, move the blocks to the gate, Phase through & keep going to find a pie piece.
NOTE:
Swim is not required, as I previusly thought.
Many thanks go out to mleach who Emailed me and notified me of that on my sr q&a page.

* 
 
 

#11:
Ability requirements: Climb & swim.
In the Human Citadel (yet again) go into the water, a lake under a bridge near a woman, swim up inside the water container and continue until you see a little water fall*, climb out on the right & look behind you, find a climbable wall, climb it & follow the hallway (this is also the short cut out of the Human Citidel ).

* 
 
 

#12:
Ability requirements: Swim & Climb & Phase.
Go to the silenced cathedral (you need Phase through the gate near the Stone henge thingy to get there) jump in the moat & go left and keep going.

#13:
Ability requirements: Constrict.
Go to Dumah's lair, go right in the room where you pushed over an obelisk to get into Dumah's courtyard, follow it & constrict a statue you should find to open secret rooms. One of them has a pie piece in it.

#14:
Ability requirements: Constrict.
Go to that big tower with a spiral staircase around it, go up it & constrict the dail in the middle of the floor to point to a doorway you wanna go into, then flip the switch to lower a drawbridge, one of the secret paths has a pie piece in it.

#15:
Ability requirements: Constrict.
In the drowned abbey just after jumping from island to island & going through a doorway, then after a few more rooms you should come into a room with four paths in it including the one you entered on, constrict the pole in the middle to drain the water, then jump down & pull out two blocks to reveal secret rooms, one room has a pie piece in it.
Until i learned about this i nearly went insane trying to figure out how to move the blocks in the water (It's so bloody obvius to constrict the pole, i'm kicking myself!)

#1:
Ability requirements: Projectile & Climb.
Go to the silenced cathederal. At the first big air vent/lift thingy Side step, climb the pipes then side step again at the portal & look around for a climbable wall, climb it & follow the hallway and look for another hallway going right, follow that one & use the projectile to break the window pane then continue & when you enter another hallway turn right, oh! and don't bother trying to phase through that gate----you can't for some reason!

#2:
Ability requirements: Soul reaver.
In Melciah's territory go across that lake where you jump from island to island (just after Melciah's portal) go through the gate on the other side, you should now be in a room with three big blocks, use the soul reaver on the block on the lower part of the room.

#3:
Ability requirements: Swim.
Go to the Rahabim portal, find yourself a way to that big boat, jump in the water & swim away from that big waterfall, go into a hole in the wall and keep swimming.

#4:
Ability requirements: Climb.
In the human city go to the waterfall that you can walk across (near the warp gate) jump & climb up the wall the water is falling down. Now face toward the main human building, jump left & ceep jumping from ledge to ledge until you reach a ledge with a glyph point orb on it, now look toward the main building again and jump across to a ledge with a switch on it......the rest is self explanatory!

#5:
Ability requirements: Constrict.
In the big tower thing that has a switch in it & numerous archways to go through, provided the drawbridge is lowered, constrict the dail in the middle of the room to point to a archway you want to go through then throw the switch to lower a drawbridge, one archway leads to a max glyph point token.