Unearthed Arcana on Bloodline Levels says
A bloodline level grants no increase in base attack bonus or base save bonuses, no hit points or skill points, and no class features. It counts as a normal class level (with no class skills) for the purpose of determining maximum skill ranks. Levels of bloodline never result in XP penalties for multiclass characters.
Include the character’s bloodline level when calculating any character ability based on his class levels (such as caster level for spellcasting characters, or save DCs for characters with special abilities whose DCs are based on class level). The character doesn’t gain any abilities, spells known, or spells per day from the addition of his bloodline levels, though—only the calculations of his level-based abilities are affected.
If a character has levels in two or more classes in addition to his bloodline levels, each class gains the benefit of adding the bloodline levels when calculating abilities. (19)
Emphasis mine. Based on the examples that follow, it's clear how bloodline levels interact with base classes. What's unclear is how bloodline levels interact with some prestige classes that also increase a base class's abilities.
If a creature with effective bloodline levels takes a level in a prestige class that increases the abilities of one or more of the creature's existing classes, does the creature add the effective bloodline levels to both the existing classes and the prestige class for determining its class level for its existing classes?
That is, does a prestige class that grants +1 level to existing class or similar benefit also increase that existing class's effective level again because of the bloodline level's effective level increase?
I know that's complicated. A few examples should clarify.
- Does a psion 5/elocator 1/metamind 2/uncarnate 2 with three fey bloodline levels have an effective manifester level of 11, 20, or another amount?1
- Does a cleric 5/arcane trickster 1/assassin 3/mystic theurge 2/thaumaturgist 1 with three fey bloodline levels have an effective assassin caster level of 9 and an effective cleric caster level of 10 or, respectively, 15 and 17, or another amount?2
- Does a binder 3/wizard 3/anima mage 3 with three fey bloodline levels have effective soulbinder and arcane caster levels of 9, 12, or another amount?3
- I didn't know where to begin for an example of effective initiator level a la the Tome of Battle. That said, an outstanding answer also determines the effective caster level and initiator level of, for example, a cleric 2/crusader 4/ruby knight vindicator 5 with three fey bloodline levels.4
I don't think any reading will endorse bloodline levels increasing anything but the creature's caster level (or initiator level or manifester level or soulbinder level). That is, I don't think there's a reading that says bloodline levels increase a creature's spells per day, spells known, power points, maximum vestige level, manuevers and stances known, or manuevers readied.5 Instead, what's at issue is the level the creature casts its existing spells (or whatever it does) because of the bloodline levels.
For instance, in the first example the creature's powers known and power points will still be as a level 8 psion no matter what conclusion is reached about the creature's effective manifester level. However, the hard part is determining that creature's effective manifester level for those powers because of the vague interaction between bloodline levels and prestige class levels that improve existing class features.
I'm aware that this issue is hotly debated and that Internet brawls occasionally erupt over this issue, so I've not linked to existing threads in an attempt to keep this agenda- and violence-free. Also be aware that the suboptimal nature of the example characters isn't the issue; I know they need all the help they can get, but I'm looking for rules.
1 To further clarify, the result could be 11: 5 levels of the base class +3 effective level from the bloodline +1 level from each prestige class. The result could also be 21: 5 levels of the base class +3 effective level from the bloodline +4 levels from each prestige class.
2 The result could be an effective arcane caster level of 9: 3 levels of assassin +3 effective levels effective levels from the bloodline +2 levels of arcane trickster +2 levels from mystic theurge; alternatively, it could be 15: (3 levels of assassin +3 effective levels effective levels from the bloodline) + (2 levels of arcane trickster +3 effective levels effective levels from the bloodline) + (2 levels from mystic theurge +3 effective levels effective levels from the bloodline). Likewise for the character's effective cleric level.
3 Tome of Magic describes the base class binder (9-16) and the prestige class anima mage (50-4). To further clarify, the result could be 9: 3 levels of each base class +3 effective levels from the bloodline +3 levels from the prestige class. But the result could be instead 12: (3 levels of each base class +3 effective levels from the bloodline) + (3 levels from the prestige class +3 effective levels from the bloodline).
4 My frustration stems from Tome of Battle's prestige classes maybe not saying explicitly that they increase (whether by +1 per level or otherwise) a creature's initiator level, so a Tome's prestige class levels might be halved for determining effective initiator level like a not-a-martial-adept base class. But I don't know.
5 An answer could try, of course. Don't let me discourage you.