A Boon

1. (obsolete) A prayer; petition.
2. (archaic) That which is asked or granted as a benefit or favor; a gift or benefaction.
3. A good thing; a blessing or benefit; a thing to be thankful for.
4. (Britain dialectal) An unpaid service due by a tenant to his lord.

(a thing received) See gift and favor

(a good thing) blessing; benefit

bane