In the new Unearthed Arcana there is a new Druid Circle, Circle of Spores, with the following ability:
Halo of Spores
Starting at 2nd level, you can launch toxic spores at other creatures. To do so, you use your reaction on your turn to deal 3 poison damage to one creature you can see within 10 feet of you. This damage increases to 6 at 6th level, 9 at 10th level, and 12 at 14th.
But accoring to the rules, a Reaction is in response to a trigger:
Certain special abilities, spells, and situations allow you to take a special action called a reaction. A reaction is an instant response to a trigger of some kind, which can occur on your turn or on someone else's. The opportunity attack is the most common type of reaction.
When you take a reaction, you can't take another one until the start of your next turn. If the reaction interrupts another creature's turn, that creature can continue its turn right after the reaction.
So what exactly are you reacting to? If it is a opportunity attack, does that mean that this Druid threatens out to 5 feet (as opposed to the normal 5)?
It also says it is only in your turn, so I guess you give up your opportunity attack? It still doesn't have a trigger, and seems like it should be a bonus action instead.