Contingent Spell

Cost: A number of sorcery points equal to the level of the spell slot

You can cast a spell to be triggered at a later time. To do so, you must spend a number of sorcery points equal to the level of the spell slot used to cast the spell. You then use your reaction to trigger the spell when the event you stipulated when you cast the spell occurs.

For example, you use your action, expend a 4th level spell slot, and spend 4 sorcery points to cast Dimension Door as a contingent spell that will take effect when a creature moves within 5 feet of you. When a creature moves within 5 feet of you a moment later, you use your reaction to trigger the dimension door and teleport to a space 200 feet away.