Do you need 3 runes open to play Call to Glory in order to spend the buff, or can you spend a buff with 0 runes open when played?

Ruling: You can spend the buff with 0 runes open when playing Call to Glory.

Sequence:

• The buff is paid as an additional cost, which is part of the finalization process of the spell
• This modifies the base cost of the spell during finalization
• All of this happens before locking in the cost of the spell and paying it
• Therefore, you do not need the three energy available to spend the buff