The mandatory attack action must be taken before any non-mandatory actions.
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Lunatic Eruption
Ⓓ Put this card on a ready minion. During their minion phase, the attached minion must enter combat with a minion controlled by their prey as a Ⓓ action unless they must hunt. Minions can burn this card as an action.
As above, and burning this card as an action inflicts 1 unpreventable environmental damage on the acting minion.
Rulings
If the minion it is on has entered combat and unlocks, he is free to take any other action.
If a minion has two of those, he is stuck and cannot act.
The action to burn it is directed at the Methuselah who controls the minion it is on. It is undirected if it is yourself.
The two actions provided are not cross-restrictive. Each can be performed once during the same turn by the same minion.