Does the Echo Knight fighter's Unleash Incarnation feature add another attack to the additional Attack action from the Haste spell?

Question

The Echo Knight fighter's Unleash Incarnation feature says (EGtW, p. 183):

Whenever you take the Attack action, you can make one additional melee attack from the echo’s position.

If the haste spell is cast on an Echo Knight, can they use their additional Attack action from haste to trigger an Unleash Incarnation attack?

The wording on the feature makes me think it's additive ("additional melee attack") and triggers after the Attack action, which is not limited by the number of attacks you can do in an action.

If this works, does it mean a hasted Echo Knight can make an additional 3 attacks, for a total of 8 attacks in 1 turn at 5th level?
(Attack action (2 attacks) + UI + hasted Attack action (1 attack) + UI + Action Surge Attack action (2 attacks) + UI)

Answer 1

Unleash Incarnation cannot exceed haste's limit

Haste states that the target

gains an additional action on each of its turns. That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action.

Haste does not set a baseline of one attack to which you can add more. Rather, haste sets a limit on the number of weapon attacks you can make with its Attack action. Hence, you cannot make both the normal attack and the Unleash Incarnation attack when you take the haste's Attack action, because that would exceed the limit of one weapon attack.

Moreover, the Unleash Incarnation attack is not some attack that occurs after the Attack action, nor is it separate from that Attack action. Rather, the Unleash Incarnation attack is part of the Attack action, so it's subject to the limits that haste imposes on the Attack action.

The above is the exact same reason why Extra Attack also can't exceed haste's limit. As a matter of fact, the relevant wording of Unleash Incarnation and Extra Attack are the same:

Whenever you take the Attack action, you can make one additional melee attack from the echo's position.

and

you can attack twice, instead of once, whenever you take the Attack action on your turn.

Answer 2

Unleash Incarnation can be used with haste

The haste spell notably limits its own Attack action to being one weapon attack only; however, Unleash Incarnation is not part of the Attack action. We can compare it to the Gloom Stalker Ranger's Stalker's Flurry feature (emphasis mine):

[...] Whenever you take the Attack action, you can make one additional melee attack from the echo's position. [...]

[...] Once on each of your turns when you miss with a weapon attack, you can make another weapon attack as part of the same action.

As we can see, when a feature adds an attack directly to the Attack action, it states this directly. Therefore, Unleash Incarnation is not part of the Attack action and is not limited by haste's "one weapon attack only" clause.

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There is also a similar question about haste and Horde Breaker (I will quote its highest-scoring answer):

• Does the Horde Breaker feature work on the attack granted by Haste?

Horde Breaker says:

Once on each of your turns when you make a weapon attack, you can make another attack with the same weapon against a different creature...

Since haste grants the ability to make one weapon attack as part of an Attack action, it will definitely be a valid trigger for the Horde Breaker ability.

This will work even though haste specifies that the Attack action can be used to take only one weapon attack, because the Horde Breaker attack is not made as part of that Attack action. It just happens to be triggered by that action, so it does not violate that stipulation.

Similarly then, Unleash Incarnation is not part of the Attack action and can be used with haste.

Horde Breaker and Unleash Incarnation use very similar wording and I would therefore treat them the same, that is, that they both can "get around" the restriction from haste.

[...] Whenever you take the Attack action, you can make one additional [...] attack [...]

[...] When you make a weapon attack, you can make another attack [...]

Answer 3

I don’t even think haste can be cast on the echo knight, haste must be cast on a willing CREATURE. Echo knight is an OBJECT.