A sombrero is the largest evil hat worn in the universe. After Darth Grievous hatched from the Chrysalis a gigantic Dark Purple Sombrero then landed and stayed attached to his head making him more smarter, more stronger with the dark side and do many evil abilities but it made him 100% Evil and souless monster. If Darth Grievous tries to remove his sombrero or his cape then Darth Grievous will be imprisoned in a Chrysalis for a whole month. His sombrero protects Darth Grievous from any aerial attacks including bomber attacks. His sombrero can also allow Darth Grievous to see invisible objects and read other creatures minds but the sombrero often makes Darth Grievous never speak english and only alien language. Darth Grievous can also hear the thoughts of the evil Sith lords including Sidious's thoughts, Dooku's thoughts and of course Banes thoughts. Darth Grievous also constructed monsterous Giant Sombrero Droids to spread fear to even the combiners and Omega Supreme. Sometimes magnaguards and death troopers wore evil sombreros to show they are specialized or show their rank among others. The three evilleros also wore sombreros and capes while the Super Evillero wore 3 of those evil sombreros on each of its three heads. In Dark Future the Sith legion wins against the Autobots and made the last of the transformers go into extinction and then Darth Grievous sealed himself in a chrysalis while his followers are placed in cocoons and after 90 years the Dark Siders hatched and Giant Sombreros landed on their heads and stayed attached to their heads making them 100% strong in the Dark side only to turn them 100% very evil.
The sombreros effect of turning Darth Grievous very evil is similar to the Teachers Hat in Kirby Right back at ya!, The Master Crown from Kirbys return to dreamland And the Chum Bucket helmets controlling the fish in the Spongebob Squarepants movie.