What happens when you need to channel 3 runes but your rune deck is empty?

Ruling: You do as much as you can, so if you can't channel runes because your deck is empty, you don't channel any.

Nuances:

• You cannot recycle runes from your rune pool to avoid this situation because channeling is not a trigger, and even with reactable triggers, your rune pool is emptied at the end of your draw phase