How the heck does fatigue and Communion work?

[Huzurdaddi]

Hmm. Well I ran a little experiment.

Test subjects: 10 communicants, 5 masters ( theurg acolytes ).

Test 1:

Masters set to : master, enslave mind, enslave mind, enslave mind, enslave mind

Fatigue cost:

Masters : 2 for each casting of enslave mind.
Slaves: 4 fatigue for each casting.

Case 2:

Casters set to : master, soul slay, soul slay, soul slay, soul slay

Fatigue Costs:

Masters: 1 fatigue per cast
Slaves: 2 fatigue per cast


Case 3:

Casters set to : master, mind burn, mind burn, mind burn, mind burn

Fatigue Costs:

Masters: 1 fatigue per cast
Slaves: 2 fatigue per cast

Woah. Not what I expeceted!

I was wrong to assume that what was happening was simply the addition encumberance. Clearly the cost can go far below encumberance. However all of the above spells have a listed cost of 20 fatigue. Their only difference is their casting requirements ( 4 astral for enslave, 3 for soul slay, 2 for mind burn ).

One of the possibilities is that Enslave Mind's fatigue cost is actually 40 not 20 and then everything works out?