Its better that way or someone might want to save our friend the orc from the nasty looking, giant leech on its back...
I wasn't able to complete it yesterday but here is the siege engine i mentioned. Got the idea to the thing while browsing through the monster manuals. Its mostly based on the corpse collector from MM3 with large influx from the hellfire engine from FC2.
Soulfurnacestats
Large Construct
Hit Dice: 15d10+30 (113 HP)
Initiative: +4
Speed: 40 ft. (8 squares)
Armor Class: 24 (-1 size, +15 natural), touch 9, flatfooted 24
Base Attack/Grapple: +11/+25
Attack: Slam +19 melee (3d8+8)
Full Attack: 2 slams +19 melee (3d8+8)
Space/Reach: 10 ft./10 ft.
Special Attacks: Breath weapon, impale, incinerate, improved grab, trample 3d8+12
Special Qualities: Construct traits, damage reduction 5/good or adamantine, darkvision 60ft., immunity to magic, low-light vision, cold iron body, searing heat, soulgems
Saves: Fort +5, Ref +5, Will, +8
Abilities: Str 26, Dex 10, Con -, Int 5, Wis 16, Cha 14
Skills: Listen +15, Spot +15
Feats: Alertness, Cleave, Improved Initiative, Improved Natural Attack (slam), Power Attack, Weapon Focus (slam)
Breath Weapon (Su):
The Soulfurnace exhales a 30-foot cone of hellfire or the ash of its former victims. It can use his breath attack once every 1d4 rounds.
Hellfire deals 4d10 damage. Reflex DC 17 for half damage.
The ash counts as paralyzing gas. Will DC 17 to negate.
Cold Iron Body (Ex):
A Soulfurnace is constructed entirely out of cold iron. Its slam attacks count as cold iron for the purpose of overcoming damage reduction.
Searing Heat (Su):
The shell of a Soulfurnace is not entirely closed and from all of its cracks and openings the heat of the raging hellfire inside can be felt. Every creature that attacks it with natural weapons, unarmed strikes or grapples with it automatically takes 2d6 points of damage from hellfire. A creature can only be affected by Searing Heat once per turn.
Impale (Ex):
If the furnace has successfully grappled a Medium or smaller creature, it can attempt to impale the creature on its back spikes by making a successful grapple check. Doing so is a standard action that does not provoke attacks of opportunity. If the Soulfurnace successfully impales a creature, the creature takes 3d8+12 points of damage and is considered pinned. Each round, the creature takes another 3d8+5 points of damage which results from the movement of the furnace and its Searing Heat.
The creature cannot break free unless it makes a DC28 strength check. Success indicates the creature is free of the spikes but takes an additional 2d8 points of damage in the process. Failure means the creature takes 4d8+8 points of damage and remains pinned in place. An ally can try to free an impaled creature with a DC 20 strength check without causing harm to it.
Once a Soulfurnace has a creature or creatures impaled on its back spikes, it is no longer considered to be in a grapple and can attack other opponents without penalty. It can not use its slam attacks against impaled opponents. Creatures that get free of a furnace become its immediate and most urgent targets. It typically pursues such creatures exclusively if it has any chance of catching and impaling them again.
A Soulfurnaces back spikes can hold up to 4 Medium creatures, 16 Small creatures, or 64 Tiny creatures. Creatures smaller than Tiny are too minuscule to be impaled on the furnaces back spikes, although the Soulfurnace can still deal 5d8+18 points of damage to such opponents by grinding them into its spikes with a successful grapple check once it has them grappled.
The bodies of creatures killed while impaled or killed by impaling still take up space on the spikes for one round after their death before they and their equipment are completely burnt to ash by the heat. Equipment made of metal or magical equipment may survive the heat and could be retrieved. The decision which equipment remains intact is up to the DM.
Incinerate (Su):
This ability works largely identical to impale but it is a full-round action and provokes attacks of opportunity. Instead of impaling a creature on its back spikes, the soulfurnace opens its chestarmor and jams the creature directly into its hellfire core on a successful grapple check. This kills the creature immediately and destroys all of its equipment. Should the furnace be interrupted by a successfull attack of opportunity or the creature succeed on a DC26 strength check the armor is opened but the soulfurnace is unable to cremate its victim. The victim still takes 4d6+6 points of damage from his proximity to the raging inferno. This counts as being effected by searing heat.
The furnace can reattempt to incinerate the creature in the next round as a standard action without provoking another attack of opportunity. There is no limit to the amount of additional attempts the soulfurnace can make but once it takes any other action then incinerate it will have to expand a full-round action and provoke an attack of opportunity again.
Improved Grab (Ex):
To use this ability, a soulfurnace must hit with a slam attack. It can then attempt to start a grapple as a free action without provoking attacks of opportunity. If it wins the grapple check, it establishes a hold and can attempt to impale or incinerate the following round.
Trample (Ex):
Reflex DC 26 half. The save DC is Strength-based.
Immunity to Magic (Ex):
A Soulfurnace is immune to any spell or spell-like effect that allows spell resistance. However, any spell or effect with the good descriptor that deals damage can affect a furnace but the furnace automatically succeeds on all saves.
One use of Raise Dead or Resurrect can be expended by a creature to make a touch attack against a soulfurnace that depletes some of his soulgems. The amount of gems affected is determined by the charisma modifier of the caster. Should the number of effected soulgems exceed the amount that is actually filled, the core of the soulfurnace is depleted and the furnace is forced into hibernation.
Soulgems (Ex):
Most constructs are basically inexhaustible and need no maintenance unless damaged but due to the excessive amount of energy that the hellfire of a soulfurnace needs this is not true for a furnace. As long as a soulfurnace remains in baator it needs neither soulgems nor an energy source since it can sustain itself the same way as devils but once it leaves it homeplane it will require fuel.
Soulgem creation
The basic material for a soulgem is a perfect ruby, worth at least 2000 GP. The process furthermore requires a the craft wondrous item feat, 80xp and a caster of at least 15th level with the ability to cast either Trap the Soul or Soul Bind.
Implantion and Designation
To integrate a soulgem into a soulfurnace it simply must be burnt by inserting it into the opened chest of the furnace. Once a gem has been implanted it is impossible to remove it again. The master of the furnace can decide if the gem will work as a fuelgem or a repairgem. The designation can not be changed later.
Charging
Whenever a creature dies while it is impaled on the backspikes of a soulfurnace, because of the impalement attack, by incineration or by the damage of an attempted incineration it can be used to charge soulgems. For every hit die of the killed creature, a single soulgem can be charged with the hit die. A creature with 4d4 and 2d8 hit die could be used to charge 4 gems with a d4 and 2 gems with an d8. The soulfurnace decides which gems are filled. Should all gems already be filled, the furnace can expand a swift action to use the hit dies immediately like an repairgem unless it already activated normal rapairgems during its current round. All dies that cannot be stored or used immediately are lost.
The stored hit dies are fragments of the soul of the killed creature. Should the creature be resurrected while a soulfurnace has still hit dies from it trapped it will lose these dies and the corresponding classlevels permanently. Should all hit dies of a creature be trapped it can not be resurrected until at least one of them is freed again. Destroying the furnace will release all stored hit dies but dies that have been used up as fuel or to repair the soulfurnace are forever lost. Should all dies of a creature be used up, this creatures soul is completely lost and it cannot be resurrected by any means, including wish or even the act of a god.
Fuelgems
To provide a soulfurnace with the needed energy, a fuelgem fuses with its core and provides it with soulfragments. Whenever the core has no more energy, it will draw one hit die from a fuel gem to keep the furnace working. A d4 provides enough energy for 8 hours, a d6 for 12 and so on. Should the core run out of energy and there is no charged fuelgem present it will instead discharge a repairgem which will provide energy for 1 hour regardless of the hit die used. Should there be also no charged repairgem, the soulfurnace goes into hibernation.
Hibernation
The master of a soulfurnace can at any time order it to go into hibernation to preserve fuel. To awaken a furnace, regardless of the reason it went into slumber, a special ritual must be performed. It takes 6 hours to perform this ritual and one or more creatures must be sacrificed by impaling them onto the backspikes of the soulfurnace. The cumulative hit dies of the sacrificed creatures must equal at least 24 hours of fuel. All of this energy will just wake the furnace, not actually provide fuel but additional sacrifices can be stored in the soulgems of he furnace as usual.
Should the soulfurnace not receive more sacrifices then needed and not have any charged soulgems it will remain active for 1 minute after the ritual and then go back into hibernation if not provided with fuel.
While hibernating, the soulfurnace looses all of its supernatural properties, is unable to move or make other actions and appears to be just an oversized suit of armor. A DC 20 Knowledge(religion), Knowledge(the planes) or Knowledge(arcana) can reveal its true nature.
Repairgems
Instead of providing fuel, a soulgem can fuse with the armor of a furnace and use stored hit dies to heal damage that the soulfurnace sustained during battle. Once per round as a swift action, the furnace can activate as many repairgems as it wishes to heal damage. Roll the stored dice to determine the amount of hitpoints healed.
A soulfurnace that activates 4 gems with 2d4 and 2d6 stored will heal 2d4+2d6 points of damage.
Construction
A soulfurnaces body is crafted from 1000 pounds of cold iron that was treated with special mixture of brimstone, sulfur and acids found only in the nine hells and costing at least 6000 GP. Assembling the body requires a DC 20 Craft(armorsmithng) or DC 20 Craft(weaponsmithing) check. Before the enchantment can begin the body must be blessed by divine spellcaster dedicated to Mephistopheles or a devil that swore loyality to him.
CL 15th; Craft Construct, limited wish, planar binding, polymorph any object, caster must be lawful evil and at least 15th level; Price 50000 GP; Cost 30000 GP + 1,600 XP + 1 soulgem (the core)
After the successful enchantment the soulfurnace is at first in hibernation and must be awakened unless it was crafted completely in baator.