Gaining experience with the power of Eternal Darkness?

[Vampireshado]

This may be an old question but I couldn't find a discussion on it anywhere. So say that somehow I'm a Dusk Giant. I'm the DM or I don't care that the Dusk Giant has no LA and isn't suited for play or I permanently polymorph into one or what have you. This would effectively make my ECL seven or plus LA whatever. Some static number. Then I go eat a village or two and get up to 24 racial HD from it's consumption ability. What happens if I gain a negative level and the level gets permanently drained?

From the SRD:

A character who loses a level instantly loses one Hit Die. The character’s base attack bonus, base saving throw bonuses, and special class abilities are now reduced to the new, lower level. Likewise, the character loses any ability score gain, skill ranks, and any feat associated with the level (if applicable). If the exact ability score or skill ranks increased from a level now lost is unknown (or the player has forgotten), lose 1 point from the highest ability score or ranks from the highest-ranked skills. If a familiar or companion creature has abilities tied to a character who has lost a level, the creature’s abilities are adjusted to fit the character’s new level.

The victim’s experience point total is immediately set to the midpoint of the previous level.

Do I immediately gain a ton of experience? What happens if I then lose all my racial HD from starving? I'm not losing any experience so would the racial HD just slowly replace itself with class levels as I lost them?

[Endarire]

If you're the GM, I recommend having permanent negative levels affect your base HD   This means more if you're form changing into said Dusk Giant.  If you are natively a Dusk Giant, same deal - apply the penalty to your pre-consumption stats.