Twilight Thorn

The Twilight Thorn is a Nobody that is found in Kingdom Hearts II. It is one of the bosses at Twilight Town.

Kingdom Hearts II
A giant Nobody who Roxas fought at the Station of Awakening

Although it tried to capture Roxas with its thorns, it was overpowered and defeated by the strength of the Keyblade master.

Kingdom Hearts II
Only one Twilight Thorn appears, when Roxas goes to the Station of Awakening. It is interesting to note that when Roxas senses a presence and turns around to see who it is, he sees a figure wearing a black cloak, before it transforms into the Twilight Thorn, just as in Sora's own Dive to the Heart, he turned to see a Shadow Sora which became a Darkside.

Strategy
Only attack its head, as that is the only weak point. It begins by tossing Roxas into the air to hurt him - use the Reaction Commands at the right time - Key Counter and Lunarsault in particular. Then follow up with Break Raid, when on the ground do a combo. It will get up and begin to spam Tendrils of Darkness.

Many of Twilight Thorn's attacks can be reflected.

When it fires thorns use the Reaction Command, Reversal to get close to attack. But if it continuously fires thorns, even if you are close to its head, prioritize safety. Keep on using Reversal until it is safe to attack. The Twilight Thorn has a tendency to shift its shape, and sometimes you may see it upside down. Again, it will fire thorns. Keep on using Reversal, then attack his head twice and begin avoiding again.

When on low health it will summon Creepers to fight. Avoid the Creepers and continue to attack.

As the fight with Twilight Thorn takes place at the beginning of the game and Roxas' stats are low, it is advisable to train him up to at least Level 5 and stock up more than three Potions. Use the Auto-Reload function and heal when necessary - because poor evasion of the thorns can take a toll on Roxas' health.

Trivia

 * The Twilight Thorn battle shares many similarities with Darkside, a gigantic Heartless. Both appear in Roxas and Sora's Awakenings, respectively, and are the first bosses of the game. Their Japanese names, Twilight Zone and Darkside, are both science-fiction horror serials.
 * The Twilight Thorn is not registered in Jiminy's journal until you enter the Simulated Twilight Town.
 * The Twilight Thorn shares its Nobody Thorn attack with the final form of Xemnas.
 * The Twilight Thorn is the only boss level Nobody shown so far who is not a member of the Organization.
 * In the cutscene before the battle with this Nobody boss, an unidentified man in Organization XIII's signature black cloak can be seen in the shadows. It is strongly believed that this man is Roxas's Organization self, similar to how the Twilight Thorn's supposed Heartless counterpart, the Darkside, first takes form from Sora's shadow.