They may appear as a new-in-town merchant with a slight golden glow over his head, or a very prim and proper older noblewoman with an unnatural glow in her eyes. Or a wheel within a wheel within a wheel, carrying a rather nice attache case.
But businesslike. Always, unmistakably, very businesslike.
They have a proposition for you. An arrangement of mutual benefit. A chance to change the world and disrupt the adventuring business. A bold new free-market solution to an ever-changing spiritual landscape.
They would like to buy a piece of your soul. Just a minority stake, mind you. Your soul would still be yours, or at least you'd be in charge of it.
They can offer you power, both mundane and divine. All they want in return is for you to do good– and let them have a piece of the action.
They will give you experience points– as many as you would need to get from your current level to the next one if you had just reached your current level. So if you're level 2, which took 2000 xp, and level 3 is 4000 xp, then they'll invest 2000 xp in you, even if you're currently at 3000.
They'll also grant you one divine blessing– they'll offer you one of their choice.
Blessings of the Angel Investors
1- You can turn spiritual enemies as a cleric
2- Your tears are holy water
3- You can never get sick
4- Once a day, you can turn a single ration into enough fish and bread to feed CHA people
5- All of your attacks count as magical and holy
6- Lay on hands as a paladin
7- Sense evil as a paladin
8- Roll a random cleric spell, you can cast it once a day
9- You carry a vague aura of holiness about you; +2 on reaction rolls with the good and devout. Not all priests are good or devout.
10- Re-roll your first failed save each day
In return, the angel investor takes 20% of all XP you earn. You also earn XP differently– you no longer get any XP for evil acts, including fighting good enemies (or neutral ones if you picked the fight unnecessarily), or looting treasure from those same enemies. XP for combat against evil enemies is 10x higher, and you may get XP for other good deeds. XP for morally neutral acts, including fighting in self-defense, exploration, or non-evil looting, is unaffected.
You may be able to bargain for a bigger XP investment, or a different blessing, if you can convincingly argue that your soul is undervalued. In extreme cases you may even be able to get two blessings.
But you can never bargain down the investor's price. It is what it is. Heaven needs to make a return on its investment, after all.
Yes, the rules about what constitute good and evil XP sources are a little vague. But you can trust an angel to deal fairly with you. They certainly have no intention of changing the rules– or the blessing– later on.
In any case, you can buy the investor out any time you you gain a new level– just sacrifice the amount of XP it took to reach that level from the last level (so if level 3 is 4000 and level 4 is 8000, then sacrifice 4000 xp when you reach level 4), stay at your current level a while longer, and your soul is yours again, free and clear. That does of course mean you lose the angel's blessing.
Rumors of demon investors, who provide infernal blessings and incentivize evil acts, are heresy. There are no demon investors. There are certainly no demon investors masquerading as angel investors.