One of the key challenges for playing the expansion is how to manage the Spirit Eater curse. If your spirit energy meter depletes too much, your character will suffer significant penalties to attributes and take periodic hit point damage as well. Consuming too much and too often will mean that your craving will increase, which in turn will mean that your spirit energy will deplete faster. I now offer some commentary on each available Spirit Eater power, and how each can fit into a gameplan for managing the curse.
Devour Spirit
Your staple spirit eating power, which you'll automatically start with. It can be used on a single elemental, telthor spirit, or incorporeal undead. The optimum use for this and similar powers is to use it on a creature that is at 'near death' but still has a significant amount of hit points left. Devour Spirit can then be used as a killing blow, and will also absorb any remaining hit points that the target has as extra spirit energy for yourself. For example, if a target spirit is 'badly wounded' and almost but not quite 'near death', a good tactic is to peck it down a little with something like a Magic Missiles spell. The next course of action, assuming that it was enough to bring about 'near death', is to then unleash Devour Spirit as a killing blow.
Provoke Spirits
This is the power you use if you want an otherwise neutral Telthor spirit or elemental to go hostile, so that you can turn it into your next snack. You'll also automatically have this power at the start of Act II.
Mold Spirit
This power is obtained when the Clay Golem in the Shadow Veil Theater is revived. It can be used in combination with Brilliant Spirit Essences to add lower-tier enchantments to your items. Simply place the item you want in the Enchanter's Satchel, along with the number of Brilliant Spirit Essences that you want to use, and then use Mold Spirit on the Satchel.
Suppress
Another power that you'll automatically start with once Act 2 begins. It can be used to restore a small amount of energy and reduce craving at the same time. Suppress will result in more energy replenished and a greater reduction of craving when a greater number of 'edible' spirits are within the radius of Suppress when it is used. The +3 Lawful points with each use of Suppress is also removed with the latest release, so you need fear no longer if you're playing a Chaotic character.
One thing to note is that using Suppress is mutually exclusive from other spirit powers. Once you rest up and use Suppress, you cannot use other powers like Devour Spirit and Eternal Rest and Devour Soul for the rest of the day. And vice versa.
This is the key power to use if you feel the need to reduce your craving, like for example having used Devour Spirit multiple times in a single day. The best spot to use it in for purposes of reducing craving is the Telthor Sanctuary in the Ashenwood.
Lastly, if Suppress is going to become a key part of your strategy for managing the curse, then it helps to get on Okku's good side. High influence with Okku will mean bonus feats for your character that will increase both the energy replenishment and craving reduction when Suppress is used.
Eternal Rest
This power is obtained by granting final rest to the undead Priest of Mulsantir in the Death God's Vault. Much like Devour Spirit, except that it can be used on incorporeal and corporeal undead. Multiple uses in the same day also will not increase craving. Its utility is for the most part limited to the Death God's Vault in Shadow Mulsantir.
Devour Soul
Can be obtained by learning it from U'Juk in the Wells of Lurue after devouring Okku at the conclusion of Act I. Note that sparing Okku will mean committing yourself to not obtaining this power, as U'Juk will consider showing Okku mercy proof that you're unworthy of what he has to teach. Devour Soul is equivalent to Devour Spirit, with the difference that its use is directed towards devouring the souls of humanoid creatures.
Bestow Life
Can be obtained by healing the Wood Man in the Ashenwood. It basically allows you to give up spirit energy to heal a wounded party member, in exchange for a reduction in craving. Sounds like a nice idea. The problem is that opportunities to use it tend to be few and far between. Suppress represents a more reliable method of reducing craving.
Spirit Gorge
Can be obtained by devouring the Wood Man in the Ashenwood, and thus is mutually exclusive from obtaining Bestow Life, and vice versa. It is the key target power for an evil character. A character who plans on obtaining Spirit Gorge must pretty much commit to having One of Many as a party member instead of Okku. Okku will instantly go hostile and attack if you attempt to devour the Wood Man in his presence. On the other hand, having a high influence with One of Many will result in bonus feats that increase the power of Spirit Gorge.
The function of Spirit Gorge is that it expands the reach of the Devour Spirit and Devour Soul (if you have it) powers. You can basically aim Spirit Gorge like you would a Fireball, also having the equivalent area of effect, so that all creatures caught within have their spirit energy drained. If multiple creatures within the area of effect are 'near death', Spirit Gorge will result in a death blow for them and that in turn means more spirit energy for your character. That also means a commitment to keeping your craving maxed out. An evil character will reason that the massive energy returns from using Spirit Gorge will more than make up for the faster energy drain from a maxed out craving.
There is in effect a well-known tactic for getting the most out of Spirit Gorge. Gann can hit a horde of humanoid creatures with Mass Drown. A Spirit Eater character with both Devour Soul and Spirit Gorge can then use Spirit Gorge to get a huge return on spirit energy.
Malleate Spirit
The equivalent of Mold Spirit, except that it can utilize Pristine Spirit Essences for item enchantments.
Ravenous Incarnation
Can only be obtained by using Devour Spirit on Myrkul in the Boneyard. The power basically allows your character to adopt a form with increased physical attributes and powerful physical attacks which have a chance to drain to spirit energy (and replenish yours at the same time) from its targets. As a method of recouping spirit energy, it isn't that much to write home about. Its distinct advantage is that it can allow you to drain spirit energy from creatures that may enjoy immunity to your other Spirit Eater powers. That in turn means you could possibly collect unique creature essences for crafting that may otherwise be unavailable to you. I'll explain in more detail how that works when I explain how Valeria is able to collect the essences of the Slumbering Coven in the Coveya Kurg'annis.