Agreement about Charity
 

Imagine the situation: a low level player, seeing in my hand a Door card (let it be a Thief), offers next - "I'll give you now this Item, and you, during your Charity phase give me your Thief card," I agree, get Item and following our agreement - give him my Thief during Charity.

Is it legal?

Re: Agreement about Charity
 

If it would be legal to give him that card as part of Charity -- you need to discard excess cards and the other player is lowest Level -- then I don't see anything wrong with that sort of agreement.

However, nothing in the rules discusses an agreement of this sort, so if the Charity giver backs out of the agreement, or the agreement itself becomes invalid for one reason or another, there's no recourse under the rules. Basically, it's a very specific house rule.