Ready Action

Designate an Action you wish to take when
a trigger of your choosing occurs. When that
trigger happens, you may choose to spend
your Reaction to take your Ready Action.
You are not required to take your Ready
Action on trigger if you do not wish to do so.
If your Ready Action is a Spell, it must have
a casting time of 1 Action. You must
concentrate until the trigger, or it is lost.