Mordenkainen's Lost Notebook
3-level Divination
Choose a willing creature within range. You may also target an unwilling creature within range; if you do so, that creature can avoid the spell’s effects if it succeeds on a Wisdom saving throw. As part of casting the spell, you must designate a particular action. If the target engages in or commits that particular action during the spell’s duration, you are instantly alerted of that fact, regardless of the distance between you and the target, even if the target is on another plane of existence. For example, you could command the spell to alert you if the target casts a spell or kills someone. You do not necessarily know the precise details of when, how, or where the target committed the designated action; you only know that it did so.