Tips & Hints about Spirit meter (can be handled easily)
I have finished MOTB without using any devour spirit or satiate ability. Here are some pointers you should read which could help you
1. Make sure in Act 1, you have entered the Death God (Myrkul)'s Vault and started a quest with a priest. I believe he is at northeast side of the map when you enter Death God's vault. Later on, when you have the spirit-eater ability(after fighting Okku) come back and talk to the priest. Along the dialogue, you will get a chance to use "Eternal Rest" which is exactly like devour spirit but used on undead.
* Eternal rest does not increase craving and effective then suppress
* After this event, you will acquire this ability. However, it can't be used on the undeads you have summoned
2. Amount of spirit energy u can gain by Suppress depends on number of "spirits" you have around you. This means you can use Gann and Kyelan to use summon creature IX to summon elementals around you. Select yourself (right click on your character) and suppress. You will get about 3 more spirit energy.
* make sure you use suppress every opportunity you have to decrease craving.
* also suppress, devour spirit, Eternal rest abilities can be upgraded by your companions depending on your influence on them. I don't remember who is who, but I know Okku is responsible for improving suppress ability.
******* IMPORTANT *********
3. Remember... when you try to travel, it will tell you how much days will be spent to get where you want to be. When 1 day passes by you can use spirit eater abilities agian.
My point is travel in a short distance.
(for example, say u are trying to get to Immi vale from Mulsantir. Do not travel directly. Travel to the Well of Lurue first which will take 2days. Use suppress, then travel to Ashenwood, suppress... etc)
There are more abilites in spirit eater class you will discover later on in the game, but above hints should be sufficient enough to help you.
P.S. when you have the lowest craving and traveling to someplace for 2 days, suppress should bring your spirit meter back to 100. (assuming you have started from 100)