If I control Kykar, Wind's Fury and I want to cast Obelisk of Urd, can I tap three spirits to convoke and sacrifice those same three spirits for three red mana to cast Obelisk?
No, this doesn't work.
While you're allowed to pay the costs of a spell in any order (barring rare exceptions), you have to generate any mana you want to use to pay for the spell before you start paying costs.
Since making mana from the spirits would require sacrificing them, you can't have your cake and eat it too in this scenario.


















