This question is inspired by the following one: Can an Echo Knight with the War Caster feat use cantrips for opportunity attacks made by their Echo?
When a creature that you can see within 5 feet of your echo moves at least 5 feet away from it, you can use your reaction to make an opportunity attack against that creature as if you were in the echo's space.
And the third benefit of the War Caster feat states (PHB, p. 170; emphasis mine):
When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack.
I am aware that the spell cast using War Caster does not count as an opportunity attack. And this makes me unsure what happens when a creature provokes an opportunity attack from the echo, but the fighter chooses to use War Caster to cast a spell instead.
When an enemy provokes an opportunity attack by moving away from my echo, and I use War Caster to cast a spell instead, where is the spell cast from?
- Is the spell cast from the echo's space, because the opportunity attack would have been made from that space?
- Is the spell cast from the fighter's space, because Manifest Echo only allows opportunity attacks to be made from the echo's space (and not spells)?
- Or is something else the case?