Note: You can be Tractored through the door @ (E-8) and Raised on the other side. Very handy when getting someone else the key. Just use the elevator at the bottom of the stairs in Delkfutt's basement to get to the 10th floor; you can also have the person(s) run to the top of the stairs and receive the drop from Porphyrion without getting in harm’s way.
Note: Because the key drop is on the Upper Tower, and you start in the basement, it is NOT POSSIBLE to just have someone wait outside the door and have another member get the key drop, as you are technically in different zones. Also, if you are the higher level doing this for a lower level, the stairs going up go to a dead end, so you will have to tractor all members who require a key and THEN trek up the tower to the top floor to kill the NM for the key.
There are 10 floors in the Tower divided into 3 parts linked by teleport. Here are the locations of the stairs/teleports:
1st Floor: E-6/F-6 Stairs (NW)
2nd Floor: I-9/J-9 Stairs (SE, dead-end at H-9, go east first)
3rd Floor: G-6 Teleporter
4th Floor: I-6 Stairs (NE, dead-ends at G-7, H-9, J-9, go the long way around)
5th Floor: H-9 (S, dead-end at I-10, go all the way around-west first)
6th Floor: J-10 Teleporter (SE)
7th Floor: F-6/7 Stairs (NW)
8th Floor: (1st time): I-6 Stairs (NE)
9th Floor: (1st time): J-10 *don't drop down the hole at H-10. (SE, this sends you back to 8th floor)
8th Floor: (2nd time): F-9/G-10 -> 9th Floor
9th Floor: (2nd time): F-6 -> 10th Floor Teleport marker on the map.
Porphyrion will drop 6 Delkfutt Keys and has a 10-minute respawn.
To access the basement quickly from the 10th Floor, trade the key to the circular area marked "Elevator" in the same room where you fought Porphyrion. This will take you to a winding stairwell leading down to the basement.
Once in the basement, cross the large room to a small room at L-9 and trade the Delkfutt Key to the Cermet Door for a cutscene.