Dragon Booster Gear

[Aleolus]

So, I recently watched through Highschool DxD, and I am wanting to make a DnD equivalent to Issei Hyoda's sacred gear. An ancient relic obviously, I'm hoping for some tips and pointers for it.

For those of you who haven't seen the show, here is a brief summary of what powers it has, as I understand them.
1) Boost
This ability increases the bearers power exponentially, and theoretically infinitely. The only actual limit is how much power their body can withstand

2) Transfer
This allows the bearer to transfer some or all of the accumulated Boosts into one or more other targets. These other targets have their own limit on how much power they can handle, based off their own bodies limits.

3) Explosion
This ability converts all accumulated Boosts into a single powerful strike.

Issei can also use it to give himself some badass armor (his Balance Breaker) and to gain so much power he could easily destroy God (Juggernaut Mode, runs the risk of killing him if he uses it too much or for too long). I plan on having both of these be unlockable abilities, which can be gained at higher levels

[Uncle Pine]

Sounds like you want a character in heavy armor who has contracted Festering Anger.

[Prime32]

Maybe a psionic sinew symbiont (Fiend Folio) with levels in wilder? Take the Psicrystal Containment and Burrowing Power feats, and learn bestow power and psychofeedback. Shout "BOOSTO!" whenever you or your psicrystal gains psionic focus, and "EXPLOSION!" whenever you expend both focuses at once (e.g. to apply two metapsionic feats to the same power).

Have your host take Deep Impact or Unavoidable Strike, as well as Psionic Unarmed Strike (http://www.d20pfsrd.com/psionics-unleashed/feats/psionic-unarmed-strike-psionic) if PF psionics are on the table.

For Juggernaut Drive, hand an item with Berserking Sword (http://www.d20srd.org/srd/magicItems/cursedItems.htm#swordBerserking) enchantments to your host then manifest form of doom.

A sorcerer build could also be an option.

[Aleolus]

Good suggestions, but not exactly what I was wanting. I was thinking a relic/artifact that anyone could potentially use, not something focusing on psionics or spellcasting.

The thought did occur to have the boost effect be granting ghost levels, in that they give bonuses to HP, skill checks, ability scores, attack rolls, damage rolls, and saves, as well as class features based on level (Psionics and spellcasting included, but also including things like Smite, a Monks Unarmed Strike damage, and so on)

[MisterKaws]

Good suggestions, but not exactly what I was wanting. I was thinking a relic/artifact that anyone could potentially use, not something focusing on psionics or spellcasting.

The thought did occur to have the boost effect be granting ghost levels, in that they give bonuses to HP, skill checks, ability scores, attack rolls, damage rolls, and saves, as well as class features based on level (Psionics and spellcasting included, but also including things like Smite, a Monks Unarmed Strike damage, and so on)

The things you mention there would really only be possible by granting divinity ranks, and no sane DM will do that unless they're doing a campaign made with the intention of turning players into demigods.