Vibrant Reverie/Arborix

Arborix is a Pre-Hardmode, spawned with. It's a large green Phoenix that resides in Underground Jungle, able to withstand huge amount of damage and revive stronger than before.

Spawn
It can only be spawned with, which can be crafted or rarely dropped by Hornets. It can be only be used in Underground Jungle.

Behavior
Arborix is a flying enemy, flying over the player. Normally, it shoots a bomb against the player that, when it explodes, shoots fast-growing and long thorns in random direction. It then rams the targeted player for a while and then returns to shoot bombs.

Dealing too much damage in a short time will make it become ethereal, becoming invincible for a short while. It then reappear and can be damaged again. After becoming vulnerable again, Ardorix rams the player while exploding itself, with explosions creating thorns that deal moderate damage to the player. To prevent this, players must stop deal damage to Arborix for a while, encouraging short-burst damage. However, you can freely damage Arborix while it's exploding and ramming at the same time. After a while, it returns normal.

In Expert Mode, Arborix can withstand more damage before becoming ethereal. This is to compensate the health increase, and increases with more players that join the fight.

Trivia

 * This boss refers to the Junglix from the Reborn Mod.
 * Furthermore, the boss was originally named Jungix from said mod.