Thing Type 420, Flame Shield Monitor, is a Monitor that gives the player the Flame Shield upon destruction. This shield protects the player from all fire damage and lava. When a player with this shield presses the Spin button in mid-jump, they will quickly dash forward, pushing their momentum towards the camera's direction like a weaker, less abrupt version of Sonic's thok. As a character that cannot spin like Amy Rose or Fang, the ability will put the player in a spin state, allowing them to damage enemies but not roll under narrow gaps. The Flame Shield will disappear when the player is submerged in water, unless the player is invincible, is Super, or is in lava. Because it disappears before the player is hurt, they will lose their rings in damaging liquids even when carrying a Flame Shield. Haunted Heights Zone is the only level in the game to feature this shield.
Checking the Ambush flag turns this monitor into a Weak Random Monitor, while checking the Special flag turns this into a Strong Random Monitor. Neither of these are recommended however as both WRMs and SRMs can't spawn Flame Shield Monitors.
This Monitor type also comes in a gold variation, Thing Type 450, Flame Shield Monitor (Respawn), which will give the player the Flame Shield once popped, before respawning after about 3 seconds. SRB2 itself does not use the Flame Shield Monitor (Respawn), but it is still available for custom maps.