Hogaak, Arisen Necropolis

• WOTC Official Reminder Textofficial rules
  Delve — Each card you exile from your graveyard while casting this spell pays for .
• WOTC Official Reminder Textofficial rules
  Convoke — Your creatures can help cast this spell. Each creature you tap while casting this spell pays for or one mana of that creature's color.

• WWizards of the Coast2021-03-19
  Official Ruling
  Because delve isn't an alternative cost, it can be used in conjunction with alternative costs, such as flashback. It can also be used to pay for additional costs that include generic mana.
• WWizards of the Coast2021-03-19
  Official Ruling
  Delve doesn't change a spell's mana cost or mana value. For example, Treasure Cruise's mana value is 8 even if you exiled three cards to cast it.
• WWizards of the Coast2021-03-19
  Official Ruling
  You can exile cards to pay only for generic mana, and you can't exile more cards than the generic mana requirement of a spell with delve. For example, you can't exile more than seven cards from your graveyard to cast Treasure Cruise unless an effect has increased its cost.
• WWizards of the Coast2024-01-12
  Official Ruling
  Tapping a multicolored creature using convoke will pay for or one mana of your choice of any of that creature's colors.
• WWizards of the Coast2024-01-12
  Official Ruling
  Because convoke isn't an alternative cost, it can be used in conjunction with alternative costs.
• WWizards of the Coast2024-01-12
  Official Ruling
  You can tap any untapped creature you control to convoke a spell, even one you haven't controlled continuously since the beginning of your most recent turn.
• WWizards of the Coast2024-01-12
  Official Ruling
  When calculating a spell's total cost, include any alternative costs, additional costs, or anything else that increases or reduces the cost to cast the spell. Convoke applies after the total cost is calculated. Convoke doesn't change a spell's mana cost or mana value.
• WWizards of the Coast2024-01-12
  Official Ruling
  If a creature you control has a mana ability with in the cost, activating that ability while casting a spell with convoke will result in the creature being tapped before you pay the spell's costs. You won't be able to tap it again for convoke. Similarly, if you sacrifice a creature to activate a mana ability while casting a spell with convoke, that creature won't be on the battlefield when you pay the spell's costs, so you won't be able to tap it for convoke.
• WWizards of the Coast2024-01-12
  Official Ruling
  Tapping an untapped creature that's attacking or blocking to convoke a spell won't cause that creature to stop attacking or blocking.

Rulings via Scryfall

• WO
  Wizards of the Coast2019-08-26

  Hogaak, Arisen Necropolis was banned in modern on August 26, 2019. Since then, the results of Mythic Championship IV in Barcelona, several Grands Prix, and other tournaments have shown that Hogaak continues to have a high win rate and oppressive effect on the metagame. In looking at the evolution of the archetype over time and the variety of successful ways to build the deck, it's clear that the card Hogaak, Arisen Necropolis is the crux of the problem. Therefore, Hogaak, Arisen Necropolis is banned. Source: https://magic.wizards.com/en/news/news/august-26-2019-banned-and-restricted-announcement-2019-08-26