Korvold, Gleeful Glutton
Legendary Creature — Dragon Noble
This spell costs 
less to cast for each card type among permanents you've sacrificed this turn.
Flying, trample, haste
Whenever Korvold deals combat damage to a player, put X +1/+1 counters on Korvold and draw X cards, where X is the number of permanent types among cards in your graveyard.
Francisco Miyara
Rulings
The cost-reduction ability of Korvold, Gleeful Glutton doesn't change its mana cost or mana value, only the total cost you pay. Specifically, the mana value of Korvold, Gleeful Glutton is always 8.
(wotc • 2023-09-01)
Korvold's cost-reduction ability doesn't affect the colored mana in its mana cost. It can't reduce its cost to less than {B}{R}{G}.
(wotc • 2023-09-01)
The permanent types are artifact, battle, creature, enchantment, land, and planeswalker. Things like "legendary" or "snow" are supertypes, not types. "Token" is not a type.
(wotc • 2023-09-01)
Rulings
The cost-reduction ability of Korvold, Gleeful Glutton doesn't change its mana cost or mana value, only the total cost you pay. Specifically, the mana value of Korvold, Gleeful Glutton is always 8.
(wotc • 2023-09-01)
Korvold's cost-reduction ability doesn't affect the colored mana in its mana cost. It can't reduce its cost to less than {B}{R}{G}.
(wotc • 2023-09-01)
The permanent types are artifact, battle, creature, enchantment, land, and planeswalker. Things like "legendary" or "snow" are supertypes, not types. "Token" is not a type.
(wotc • 2023-09-01)