That'll do.  I think we can use the same text for both master and minion.
		
		
	 
Updating the 
Bone Tyrant Working Draft.
	
		
	
	
		
		
			Any ideas for background?  About all we've got is that they're native to the 9 Hells and are often used to protect evil shrines.  Probably it's worth determining what spells can summon them at what caster levels --- I don't recall figuring that out yet.  Any ideas?  I'd probably go with planar ally to get the master, and maybe the minions come for free? That seems like skirting the rules a bit.  But even greater planar ally doesn't allow all the HD needed.  Gate? Seems too high-level.  Write a new spell?  Too much trouble?
		
		
	 
Well since their main power is rebuking undead, while on the Nine Hells I'd guess they are used as undead overseers on the Nine Hells, driving hordes of undead about various tasks at the behest of some powerful Devil.
As for how to summon them, the original adventure says "evil priests, in a spiteful act, entered it and summoned the 
Master Bloody Bones".
That tells us they can be summoned by (evil) clerics and it may take more than one to do so, since it uses the plural "priest
s".
We could use the 
planar ally series and allow the minions to be summoned separately - e.g. it requires a 
planar ally or 
greater planar ally for the Master and either six 
lesser planar ally spells, three 
planar ally or two 
greater planar ally spells for the Minions, so the pact requires a head priest to summon the master and between two and six assistant priests to summon the minions.
Hold on though. The 
planar ally is a Calling spell, not a Summoning, and the flavour of the original suggests it's a summoning, since the Bone Tyrants disappear when the conjuration is broken.
That suggests we either need to create a new spell or make it a specialized application of 
monster summoning. We could modify the Unholy Sentinel and Unhallowed Aura special abilities to allow for the binding.
It'd probably require 
monster summoning VI to summon a Bone Master and a 
monster summoning III for a Minion.
Furthermore, I think it'd be nice to let a "free roaming" bone tyrant still have an unhallowed aura, but with a reduced radius.
Incidentally, reading the original adventure there's no mention of an unholy altar, the Master Bones is simply bound where it was originally summoned. We could edit that detail out of the Unholy Sentinel description, but it just feels right.
So, how about the following modification...
A bone tyrant master can be summoned with 
summon monster VI, a master and up to six bone tyrant minions can be summoned with a 
summon monster VII.
A bone tyrant minion can be summoned with 
summon monster III.
Unhallowed Aura (Su): A bone tyrant master continually radiates an effect similar to the 
unhallow    spell. When not serving as an Unholy Sentinel (see below), a bone tyrant master's Unhallowed Aura is a 40 ft. radius emanation that moves with the bone tyrant.
If a bone tyrant master agrees to serve as an Unholy Sentinel , its Unhallowed Aura is centered on the 
unhallow spell used in the Unholy Sentinel pact. The unhallowed ground can have any shape as long as it is continuous and at least as large as the 
unhallow spell at its heart. Its maximum size is a radius of 100 ft. plus 10 ft. per caster level of the 
unhallow.
All turning checks made to turn undead within the Unhallowed Aura take a   profane penalty equal to half the effective cleric level of the   master's  Subjugate Undead ability. Remember that the master gains   positive levels  if any of its minions are destroyed (see Minion   Dependence), which will lower its effective cleric level. For example, a   typical master  has a Subjugate Undead level of 11, so radiates a -5   turn check  penalty. If  it loses 3 minions it gains 3 positive levels,   weakening its Subjugate  Undead to 8th level, for -4 turn check  penalty.
Note that the Unhallowed Aura's turn undead penalty does not stack with the -4 turn undead penalty of an 
unhallow spell, since both are profane penalties.
Nonmagical barriers do not obstruct an Unhallowed Aura. A 
hallow spell will block the effects of the aura, while a 
protection from evil or 
magic circle against evil spell will weaken the Aura by 2 (e.g. a -4 turn undead penalty becomes a -2 penalty).
Unholy Sentinel (Su): A summoned bone tyrant master can agree to protect an area by mystically binding itself to an unhallow effect, such as an 
unhallow spell or an unholy altar. In the case of an 
unhallow spell, this counts as the "spell effect" that can be fixed to the 
unhallow, so has a maximum duration of one year.
The bone tyrant master always requires payment consistent with the duration and danger of the sentinel duty. Until it     completes its term of service or is released from its agreement, the master may     not move outside the 
unhallow effect (normally a 40 ft. radius, like the spell). If the master is  forced  outside   that range, it is instantly teleported back to a  designated  area   adjacent to the centre of the 
unhallow effect, as if by a 
word of recall  spell.  The bone tyrant master and its minions can not travel to another plane  until the Unholy Sentinel pact expires, so cannot be banished to their  home plane by 
holy word and the like.
Should the 
unhallow effect be destroyed or broken, the bone tyrant master and all its    minions are instantly banished back to the lower planes. A typical unholy altar has hardness 8, hit points 80 and Break DC 30.