- "The Ray of Doom is a persistent solid beam of bloon destruction."
- — Official Description
Ray of Doom is the final upgrade of Dartling Gun on Path 1, costing $46750 on Easy, $55000 on Medium and $59400 on Hard. It allows the Dartling Gun to shoot a persistent beam that pops all bloons in its path.
The Ray of Doom has a pierce of 100, popping bloons every frame; even Ceramic Bloons are popped in well under a second. This upgrade is probably one of the best upgrades for popping normal Bloons, being a tower with one of the highest pierce caps in the entire game.
- Even though the description says that it shoots a persistent beam, it actually flashes, however this is purely cosmetic; the ray's area of effect is not affected by the flashing.
- Ray of Doom is similar to Death Ray Vision in Bloons Super Monkey and is likely to be based off it.
- This upgrade is notoriously bad against individual M.O.A.B. class bloons, as it has a popping pierce of 100 but only pops 1 layer per frame. This means it effectively loses 99% of it's firepower. It is still more than a match for an individual MOAB or BFB however, and indeed can take down large groups of them quickly. It only struggles against the mighty Z.O.M.G..
- The Ray of Doom used to have infinite pierce. This was changed to 100 in an update.
- A Ray of Doom can beat an entire MOAB and all bloons within it in any track. 2 of these can destroy a BFB, and 6 of these can destroy a ZOMG.
- The Ray of Doom can pop leads but the Laser Cannon cannot even though they appear to both be lasers.
- The HAZMAT suit looks like the one for a Glue Splatter Glue Gunner, but has a gas mask like the Bloon Liquefier Glue Gunner's.
- This is the second most expensive upgrade in BTD5, after the Temple of the Monkey God.
- The Ray of Doom will pierce through anything, but if it has reached its pop limit, it will still pierce through but not pop.
- The Ray of Doom only stops shooting in between Rounds. It will constantly shoot the ray during rounds, even if there are no Bloons on screen. It will also constantly shoot in Sandbox Mode. However, with the Great Divide update, it no longer fires until a bloon exists.
- This is one of the few lasers that can pop Lead Bloons. The others being High Energy Beacon, Bloonsday Device, 1/3 Robo-Monkey and Meerkat Spy Pro.
- In Bloons TD 5 iOS the Ray of Doom cannot pop lead bloons without Depleted Bloontonium Darts.