retroactive conversion of levels?

[Particle_Man]

The Blackguard class allows one, if one enters it with 11 or more levels of ex-paladin, to convert those ex-paladin levels to Blackguard levels (so one could become a 1st level ex-paladin/10th level blackguard, for instance).

Are there other classes (presumably prestige classes) that allow one to retroactively change previous class levels?

[Tzardok]

The Creeping Darkness optional rule allows conversion of levels as wizard or sorcerer into shadowcaster whenever you gain a shadowcaster level. A similiar rule exists for binders and clerics.

[Doctor Despair]

Unholy Ravager of Tiamat has a pseudo-conversion mechanic:


Divine Conversion: At 1st level, an unholy ravager loses any effective sorcerer level it had previously gained by virtue of its age and draconic variety. Its effective divine spellcasting level increases by the number of sorcerer levels it sacrificed, allowing the dragon to cast cleric spells much more effectively. These effective levels apply only to the dragon's spellcasting, not to other class abilities (such as turning undead or wild shape). For example, a very old red dragon/1st-level cleric adopts the unholy ravager of Tiamat prestige class. Its sorcerer caster level of 13th converts into thirteen effective cleric levels in addition to its 1 level of cleric, giving the dragon the spellcasting ability of a 14th-level cleric.

Likewise, so too does a Sacred Warder of Bahamut:


Divine Conversion: At 1st level, a sacred warder loses any effective sorcerer level it had previously gained by virtue of its age and draconic variety. Its effective divine spellcasting level increases by the number of sorcerer levels it sacrificed, allowing the dragon to cast cleric spells much more effectively. These effective levels apply only to the dragon's spellcasting, not to other class abilities (such as turning undead or wild shape). For example, a very old gold dragon/1st-level cleric adopts the sacred warder of Bahamut prestige class. Its sorcerer caster level of 13th converts into thirteen effective cleric levels, giving the dragon the spellcasting ability of a 14th-level cleric.

Dispassionate Watchers of the Chronepsis have a similar ability:


Divine Conversion: At 1st level, a dispassionate watcher loses any effective sorcerer level it had previously gained by virtue of its age and draconic variety. Its effective divine spellcasting level increases by the number of sorcerer levels it sacrificed. These effective levels apply only to the dragon's spellcasting, not to other class abilities (such as turning undead). For example, a very old amethyst dragon/1st-level cleric adopts the dispassionate watcher of Chronepsis prestige class. Its sorcerer caster level of 11th converts into eleven effective cleric levels, giving the dragon the spellcasting ability of a 12th-level cleric.

I think Hathrans can convert their spellcasting to Durthans? Durthan has this to say:


Spells per Day/Spells Known: ...

A character who has converted hathran levels to durthan levels retains the same allocations of caster level increase among her various arcane and divine spellcaster levels (in other words, she does not reassign these level increases when converting levels in this manner).

To speak to the heart of the question though, there is one class that does precisely this: Ronin.


Ex-Samurai Ronin Abilities
Samurai Level - Regained Abilities

1st—5th - The ronin regains any kiai smite class feature he once possessed as a samurai, and can use it just as any samurai can.

6th—10th - As above, plus the ronin regains any staredown class feature (staredown, mass staredown, improved staredown) he once possessed as a samurai, using it just as he did before he became an ex-samurai.

11th+ - As above, plus an ex-samurai of this stature immediately gains a ronin level for each level of samurai he trades in. For example, a character who has thirteen levels of samurai can immediately become a 10th-level ronin with all abilities if he chooses to lose ten levels of samurai. The character level of the character does not change. However, with the loss of samurai levels, the character might lose some of the class features granted by the samurai class. Thus, an ex-samurai of 14th level could become a 4th-level ronin/10th-level samurai, but would lose the improved two swords as one, kiai smite 3/day, and improved staredown class features.

[MaxiDuRaritry]

A lot of undead "classes" convert your class levels to "undead creature"...

[bekeleven]

I'm doing my best not to bring up the darklight wizard and failing.

[Anthrowhale]

Maho-Tsukai can convert spellcasting from previous levels into Maho-Tsukai spellcasting.

[Particle_Man]

Thanks! The ronin one has promise!

[ShurikVch]

Ghostwalk have the "life epiphany" rules: when ghost character is resurrected, they can convert their levels in Eidolon (or Eidoloncer) class into levels in any other available class (for eidoloncer - any available spellcasting class)

[daremetoidareyo]

Defiant converts cleric levels