When you use your divine smite or your banner, you drop an orb of light on the ground in an unoccupied space of your choice within 5ft of yourself, which when picked up (free action when you are on that space), contributes to filling your Ultimate Bar, which can be used to unleash the power of light in a number of different ways. Each orb is worth 1 charge per die rolled on the smite, or in the case of the banner, 1 whenever an ally starts their turn in the banner's area and when you use an ultimate, it's duration is 1 round for every 10 charges you expend. If that ability has a DC instead of a duration, the DC increases by 2 for each round expended. If an ally chooses to pick up an orb, they may expend one hit die, healing for that amount. The options for your ultimate is listed below:

Void Titan: You erect a bubble of powerful energy for your allies to stand in. The bubble emits from you in a 20ft radius, but is immobile and does not move with you. Attacks and effects cannot cross the bubble, but creatures can. Friendly creatures inside the bubble are granted temporary hit points equal to their hit points when they first enter, which immediately disappear when they are not within the radius of the bubble. Hostile creatures inside are under the effects of Hallow. You choose which effects are active when erecting the bubble.  Once you use this Ultimate, you cannot use it again until you take a long rest.

Arc Strider: You sheathe yourself in lightning energy, empowering your speed and agility. Your weapon attacks do an additional 3d8 radiant damage (which counts as smite damage for the purposes of orbs), and you may use your reaction when you would be inside of an arena of effect to use your movement, potentially causing it to miss you. When you move, you Blink to your destination, making it to the final square you would stop moving on, without ever being on the previous squares, as if you had time traveled there. Once you use this Ultimate, you cannot use it again until you take a long rest.

Nova Bomb: As an action, you unleash a bomb of pure purple void energy on an arena, lobbing it towards the enemy. Choose a space you can see within 60ft of you, as you sling the payload to that point. It explodes in a 45ft radius, and all creatures caught inside must make a STR saving throw against your spell save DC, taking necrotic damage equal to double the amount of smite dice expended for this ability, or half as much on a success. Any creature killed by this ability also explodes, making a secondary explosion with a radius of 30ft, and dealing damage equal to their remaining hit points before the Nova bomb, or half as much on a success (uses the same DC)