This can be before blockers are declared, after blockers are declared but before combat damage is dealt, during combat after combat damage is dealt, during the postcombat main phase, during the end step, or, in some unusual cases, during the cleanup step
To find this, first head to disneylorcana.com, then click on the Store Locator option, as shown
Back The Lord Master of Hell Legendary Creature - Demon Noble Wizard Starfall - Whenever The Lord Master of Hell attacks, it deals X damage to each opponent, where X is the number of noncreature, nonland cards in your graveyard
Its just great
This means that, every turn, Ursula could be playing lots of things for free or making a large inkwell
A creature with both abilities will just deal damage as though it only had double strike