shoots a deadly ring of flame instead of tacks. Also increases range.
~ BTD5 description
Ring of Fire is the final upgrade for the Tack Shooter in Bloons TD 4 and Bloons TD 5. It is a tier 4 upgrade unlocked at Rank 22. The Ring of Fire is effective against all types of bloons, but it cannot detect Camo Bloons without other special towers around it. Unlike firing in 8 or 16 directions like its previous upgrades, it shoots its fire in a solid ring surrounding the whole tower, popping bloons that touch it or come very close to it. In BTD4 and BTD5 it pops 1 layer of bloons. In BTD5, this upgrade costs $2125 on Easy, $2500 on Medium, $2700 on Hard and $3000 on Impoppable.
This tower usually has a high pop count after round 60. In BTD4, this tower is a lot more effective than a Blade Shooter. This upgrade is good for thinning out several Bloons packed together.
The Ring of Fire fires at a rate slightly faster than a Tack Shooter, and there are no holes in its range (sometimes, some of the bloons can slip between the tacks). If you pack many Rings of Fire together, even Ceramic Bloons can be popped in a few seconds, although you will need 2 at a minimum. Although not the most effective against M.O.A.Bs, they still do deal some damage to them. They usually do not perform too well when facing packed M.O.A.Bs.
In the mobile version of Bloons TD 4 the Ring of Fire has a greatly increased firing rate but does not shoot in a ring, rather with bursts of fire in 8 different directions. However, the disadvantage to this are the "holes" between the fire bursts. The advantage is that it can do extra damage to M.O.A.B. Class Bloons this way.
In a recent update the Ring of Fire is now a ring instead of bursts.
Lag can reduce the Ring of Fire's firing rate dramatically, especially when comparing it to the speed of the bloons.
The Ring of Fire has a slightly greater range than the Blade Shooter in BTD4.
This upgrade may sometimes be a downgrade in BTD5, mainly because it deals less damage to MOAB-Class Bloons, and it's weak against Ceramic Bloons, because the Tack Sprayer shoots out so many tacks each doing one damage.
This is the only upgrade for the Tack Shooter that allows it to pop Lead and Frozen Bloons in BTD4 and BTD5.
In BTD5, the icon of Ring of Fire is an explosion, instead of a flame, fire or similar.
In BTD5, this upgrade suffers a bug where its range can't extend past 4/1. If the player tries to use the Super Range Tacks upgrade, it won't hit bloons further than the range it usually has at 4/1, yet it will still activate.
If the player adds a Monkey Beacon, it still won't pop the bloons further than the 4/1 range. Same applies to the Pontoon Pro bonus.
In September 29, 2013, the Ring of Fire could pop 2 layers and up to 180 bloons per shot and its price was increased to $3500. However, on October 26, 2013, it was reverted back to original, but with a slightly faster speed.
This upgrade is the most useful for shutting down bloon rushes.Keeping 3 in a corner is enough to deter a densely packed group of RegrowCeramic Bloons.
It is very powerful when it is put in the center of a 3-sided curve.
Just like the Ray of Doom, when it reaches its popping power it will still go over the bloons but not pop them, unlike most other projectiles which vanish when they reach their popping power.
In Bloons Monkey City it is shown that the ring of fire upgrade uses thermite, an extremely hot liquid that is practically liquid metal. It would take extremely large amounts of heat and power to get the thermite as far as it does in the game.