I think the Lunatic Cultist is an important boss, and a woeful thing is that it don't have a Treasure Bag.
So I think...
In Expert Mode, after the Lunatic Cultist is defeated, it will drop a Treasure Bag. The bag contains an Expert Mode-exclusive items.
For the Expert Mode-exclusive items, I have two ideas.
1. A mount-summoning item that spawns Ancient Vision, a miniature rideable Ancient Vision-style mount that can fly and hover indefinitely.
2. A accessory that can make player hover for a period of time.
And at the same time, there is a Lightning Ritual Ring behind the player and the player will have more damage and defense during hovering.
Other
In Every Mode, after the Lunatic Cultist is defeated, one of the following 4 weappens will be dropped (1/3 chance, just like the Skeletron).
1. A Boomerang, when it hit enemies it will fire fireball that explode upon contact with the enemies.
2. A Launcher, it can fire extra bolts of lightning at the enemies.
3. A Spell book, it can fire a crystallized ball of ice mist aimed towards the enemies.
4. A Minion-summoning weapen, it can spawns Ancient Booms, just like UFO.
So I think...
In Expert Mode, after the Lunatic Cultist is defeated, it will drop a Treasure Bag. The bag contains an Expert Mode-exclusive items.
For the Expert Mode-exclusive items, I have two ideas.
1. A mount-summoning item that spawns Ancient Vision, a miniature rideable Ancient Vision-style mount that can fly and hover indefinitely.
2. A accessory that can make player hover for a period of time.
And at the same time, there is a Lightning Ritual Ring behind the player and the player will have more damage and defense during hovering.
Other
In Every Mode, after the Lunatic Cultist is defeated, one of the following 4 weappens will be dropped (1/3 chance, just like the Skeletron).
1. A Boomerang, when it hit enemies it will fire fireball that explode upon contact with the enemies.
2. A Launcher, it can fire extra bolts of lightning at the enemies.
3. A Spell book, it can fire a crystallized ball of ice mist aimed towards the enemies.
4. A Minion-summoning weapen, it can spawns Ancient Booms, just like UFO.