Mel

The chosen unit will be given -3 [M]. All other enemy units at the chosen battlefield will be given -2 [M].

Mel, Newly Awakened’s empowered ability is a replacement effect. It replaces the event of a spell or ability you control giving a unit it chooses -[M]. The event it replaces that with is the spell or ability giving an additional -1 [M].

Although Moonfall gives -[M] to multiple units, only one of them is chosen, and thus the only event that is eligible to be replaced is the chosen unit being given -2 [M]. It will be replaced with that unit being given -3 [M]. The events of the other units being given -[M] will not be affected by this replacement effect.

Relevant Rules: 370.1., 370.1.b.

Fuente: Riftbound: Vendetta Rules FAQ and Clarifications (newest FAQ found)

The chosen unit will be given -2 [M], to a minimum of 1 [M]. If it was 2 [M], it will become 1 [M].

In the case of Stupefy, Mel, Newly Awakened replaces the event of Stupefy giving -1 [M] with it giving -2 [M] instead. However, a replacement effect that replaces an event modified by the game effect that generated that event will inherit any of those modifications. In this case, Stupefy modifies the “give -1 [M]” game action and thus event with “to a minimum of 1 [M].” The replaced event will inherit the same modification.

Relevant Rules: 375.

Fuente: Riftbound: Vendetta Rules FAQ and Clarifications (newest FAQ found)

They can play Abandon targeting your spell. On resolution, they will Predict, but nothing else will happen.

Mel, Newly Awakened says “your spells and abilities can’t be countered.” If the spell can’t be countered, Abandon will attempt to counter it and fail, and then it will replace the event of it being put in the Trash with it being returned to its owner’s hand. However, that event never occurred, so there is nothing for the replacement effect to replace. Thus, Abandon will resolve to no effect. The replacement effect only functions within the limit of the resolution of the ability (it’s not a delayed replacement effect that specifies a duration), so even if the spell resolves later, it will go to the Trash as normal.

Fuente: Riftbound: Vendetta Rules FAQ and Clarifications (newest FAQ found)

In the case of Rebuttal, gaining control of a spell is not the same thing as countering that spell. Effects that prevent spells being countered don’t prevent their controller from changing. If Rebuttal is played choosing your spell, and they pay [A] during resolution of Rebuttal, they will gain control of it. However, them not paying [A] does not mean the spell will be countered.

Fuente: Riftbound: Vendetta Rules FAQ and Clarifications (newest FAQ found)

Gangplank, Naval will replace his Might being lowered with him being given +3 [M] this turn.

Swap calculates the difference in Might and generates two effects: an increase, and a decrease. When a swap effect is applied to two units’ Mights, it gives those units +[M] and -[M] respective to who has the higher Might.

Under the hood, Gangplank’s replacement effect sees the event of him being given -[M] and replaces it with him being given +3 [M] this turn instead. The event of the other unit being given +[M] is unaffected by Gangplank’s replacement effect. By the time we apply the replacement effect, the difference between the two units has been calculated. In the example with the 2 [M] unit, the final Mights of the two units will be 2 [M] → 6 [M], and 6 [M] → 9 [M].

The way this works is not immediately obvious based on how the swap game action rules are written. We will clarify this in a future rules update.

Note that this logic also applies to Mel, Newly Awakened and Switcheroo.

Fuente: Riftbound: Vendetta Rules FAQ and Clarifications (newest FAQ found)