Spell Synergy- Unseen Servant
Some of these ideas may be considered grossly overpowered, but consider the rules for synergy- each spell only lasts as long as its description. So if one was to mix an Unseen Servant (1 hour per level) with Wall of Fire (concentration +1 round per level), the caster would have to concentrate a long time to ensure the flames go out when the servant spell ends. Only increasing the spell level (using metamagic feats or spell design) can alter this. Also note that I am referencing some Pathfinder and d20 spells.
The handiest spells for Unseen Servant are from Distant Horizon. In The Practical Enchanter there is Unseen Supervisor. This spell adds skill ranks and allows for limited "aid another" checks. For those who want a lot of powerful Unseen Servants, there is the 13th level spell from Eclipse, Unseen Horde.
The one spell I would not require but some of you might is Ghost Touch. Unseen Servants are and are not incorporeal- their traits are somewhere in between. It is up to you if such a spell is needed for some of the following mixtures.
For those who want a strong Unseen Servant, then Telekinesis is the spell.
For those who want to make Unseen Servant into a weapon, then Magic Weapon or Magic Fang (depending on if the Servant is a natural weapon or not) is the way to go. One that is made with Magic Weapon could be enhanced with Magic Fang to provide a weapon quality if desired*. The Pathfinder spell Bow Spirit could be enhanced with Unseen Supervisor, increasing its BaB.
Wall of Fire and Wall of Ice (or the Pathfinder Elemental Aura) can be used to turn the servant into a weapon. It can not attack directly, but it can engulf or pass through a target and cause damage. Obviously armor is useless in such a situation... Note that if you use higher level versions of Unseen Servant that allows for more than one servant, then concentration only applies to one, but all can have the limited duration ability to fry or freeze victims.
Solid Fog can be used in a similar manner, but it allows bullrushing, limited grappling or simply slowing the target and interfearing with actions.
Cup of Dust, Feast of Ashes, Brand, Dust of Twilight, Expend (Pathfinder spells), Bestow Curse and similar spells may be transfered by an Unseen Servant, but only as a one time deal. Higher level versions of those spells allow a servant to curse anything they touch. Or it could be used for Cure X, Remove Curse and similar touch spells. Though I would suggest a higher level version of Unseen Servant to increase its range.
Spacewarp is from The Practical Enchanter and creates extradimentional spaces like a portable hole. Unseen Servant in synergy with this spell creates a servant that can "swallow" creatures and objects and move them around. A number of servants with Spacewarp could alter a battlefield enormously in a short amount of time by moving boulders, logs and other large objects.
Unseen Servants can be used to speed up spells like Move Earth. One servant reduces the amount of time by 10%. Higher level versions of Unseen Servant can create more of them and thus decrease the amount of time, to a maximum of 90%. Or, for those who want to use existing spells, Haste may be added into the mix and decreases the casting time for Move Earth by 20 or 30% (on top of the 10% of the Unseen Servant and depending on how you want to read the description of Haste). Or the Pathfinder spell Anthaul could reduce the casting time of Move Earth by an additional 10 or 20%.
Wizard's Light (from Bastion's Spells & Magic) create a light only the caster can see. Applied to an Unseen Servant, it allows the caster to have a mobile flashlight that will not attract unwanted attention.
* I have mixed spell lists a few times before and you might be wondering how to do this. The two feats in Kobold Quarterly 18 are for a lone spellcaster and for more than one. The latter feat could be used by different kinds of spellcasters to combine their powers.
Only after I wrote this did I discover that Super Genius released a short pdf of feats used to enhance Unseen Servant. Those feats used with these ideas can make for a very useful spell. And even if you don't want to take such a feat, there is always putting it into something like a metamagic rod or spell focus item (Dragon 111).
