MTGNexus

Hi, is it possible to use the black mana from tournament grounds to cast the "adventure" of adventure cards. For example, using the black mana to cast Alter Fate in Order of Midnight.

No, it is not possible. Alter Fate is a Sorcery with the Adventure subtype, and not a Knight spell.

Referencing the rulings:

When casting a spell as an Adventure, use the alternative characteristics and ignore all of the card's normal characteristics. 
The spell's color, mana cost, converted mana cost, and so on are determined by only those alternative characteristics. 
If the spell leaves the stack, it immediately resumes using its normal characteristics.

You could use it to cast Nameless Inversion or another instant or sorcery with Changeling, but other than that, instants and sorceries generally don't have creature types, and thus can't be cast with Tournament Grounds.

ok, thanks for clearing that up.