Hello to all,

I was wondering if an experienced player could help settle a question that was posted on BoardGameGeek.

The initial question was:

If, as the siren, I use "Siren's call" on a creature that is rooted (such as certain trees) i was wondering if the opponent is required to pay the mana to uproot and move or is it the opposite and that creature is effectively immune?

My reply was:

Based on the wording of the Siren's Call ability (during its action phase, a creature with the Siren's Call marker MUST move at least one zone closer to the Siren, if possible), and provided of course the Rooted creature in question has the Uproot object trait, I'd say the controller of that creature would have to move said creature (and consequently, pay the Uproot cost).

Another user chimed in, saying:

It's creature that has to move. Its controller doesn't have to make it possible for the creature to move. You don't have to pay uproot cost or grant flying to vampiress. In codex/supplement section on mandatory actions is written that You don't have to use optional abilities to do mandatory action.

I replied to this with the following quote from the Rules Supplement:

(...) The controller of the creature is not required to do anything beforehand that would make the action possible. For example, the controller does not have to activate the ability of another card (like using Archer’s Watchtower to give a ranged attack the Indirect trait) in order to make the action possible. Note that declaring the action includes paying any costs, so one would be required to pay any costs required to perform the action.

Underline mine.

This was countered again:

You pay uproot cost when activating a creature not when declaring an action. You first activate a creature and check for available actions after. This is different case from blue gremlin who can replace move action with teleport.

Can anyone help settle this question?

Thanks a lot.