I think there is a lot of ways Reflect can be incorporated into the game, and possibly be a good utility and use of the lily system for WHM. Many of the ideas mentioned here are pretty good. It can't work like in console FF games, where it generally negated all damage and sent it back at the caster. One game even made it so powerful that you could equip a trait that reflected back x2 the intended damage.

I like the idea of it mitigating damage, and sending back a certain percentage of it. I don't think it should be so strong that a mob can kill itself, but the dmg should be respectable enough for the ability to have merit. As a straight WHM ability, the lilies could be used to determine how much damage is sent back. If it is an ability only available with lily stacks then it would have to work another way since it would have a fixed amount of damage it returns.

Traditionally, reflect doesn't send back physical attacks, certain mob specials, boss one-shot mechanics and things of the like. It would have to return mob auto attacks for sure, but the AoEs I am not so sure. I'm also not quite sure making it AoE would be OP or useless. It probably should be single target.