Does Tank affect spell damage, and what happens when a unit with Tank is played as a reaction to a spell targeting another unit?

Ruling: Tank only applies to combat damage and does not affect spell damage. When a unit with Tank is played as a reaction to a spell targeting another unit, the spell damage is not redirected or prevented.

Nuances:

• Tank has no effect outside of the combat damage step
• Playing a unit with Tank in response to spell damage does not change the spell's target or prevent the damage