Taken from Shankdrakor's guide on the official forums,with permission to post it here.
Note: Colour of the chart indicates alignment of devil family: RED
for Chaos, BLUE
for Law and GREEN
The Level Range is the range of levels which they can spawn at... but the BASE level is the minimum level they will appear when fused or when negotiated with, therefore its the lowest level that you are able to gain these devils.
Note the FUSION COMBINATIONS are what you use to fuse them, NOT what fusions they can be used in, as this would make the charts useless.
When fusing the two devils together to form a new one, their average level is what determines which devil from the new family you will form, so please keep that in mind!