Rulings

• 2020-11-10
  Jeska's Will isn't a mana ability, even if you select the first mode (or both modes). It uses the stack and can be responded to.
• 2020-11-10
  Use the number of cards in the target opponent's hand as Jeska's Will resolves to determine how much to add.
• 2020-11-10
  You must follow the normal timing permissions and restrictions for the exiled cards. You can't play lands this way unless you have land plays available.
• 2020-11-10
  You'll still pay all costs for a spell cast this way, including additional costs. You may also pay alternative costs if any are available.
• 2020-11-10
  Any of the exiled cards you don't play will remain exiled.
• 2020-11-10
  Even though the card is named after a specific character, controlling any commander will satisfy its condition.
• 2020-11-10
  There's no extra bonus if you control more than one commander.
• 2020-11-10
  The commander you control doesn't have to be your commander.
• 2020-11-10
  Once you've announced that you're casting a spell, players can't take any actions until you've finished doing so. Notably, opponents can't try to remove your commander to change how many modes you may choose.
• 2020-11-10
  Once you've chosen both modes for the spell, it doesn't matter whether you continue to control a commander. This is true even if you somehow no longer control a commander as you finish casting the spell.