Time to relocate underground!
BURROW
Burrow for the Chomper is an ability that allows burrowing underground. In this state, you are completely immune to damage, except for very limited sources, and you are able to eat enemies from underground when you get close enough to them, which would instantly vanquish them. However, you cannot attack in any other ways in this state, it takes a while for this ability to resolve after activating, and your enemies have a chance to vanquish the Chomper before it eats an enemy. The delay before entering Burrow is greatly reduced in BFN. Burrow is the only way you can eat enemies in BFN, although in the GW series, there are other ways to eat your enemies. This can be used as a way to eat enemies that are alone, or to get away when being surrounded by multiple enemies or in another bad situation. I think this ability is really useful, having an efficient way to instantly vanquish an enemy or being able to escape while being immune to damage can be really useful and I like that.
GW Alternate Abilities
Sprint Burrow: This ability makes you move much faster in Burrow, although it lasts nowhere near as long as the regular version and the total distance you get out of it is actually reduced. It also easier to notice by enemies. This can be good for quick attacks that your enemies may struggle to react to or to escape even more quickly, which could be useful. I find this ability alright, you do not get as much out of it compared to the regular Burrow, although I can see some situations where it could be useful, such as attacking quickly or fast escapes.
BFN Alternate Upgrades
Hotrod (2 upgrade points): When you successfully eat an enemy with Burrow, you gain a significant speed boost for a short time, which is useful for getting away after a vanquish or approaching enemies more quickly. Additionally, you move at regular speed while digesting an enemy while completely removes the speed reduction penalty while eating an enemy. I think this upgrade is really useful, it makes it much easier to get around by eating enemies successfully and you are less vulnerable while eating enemies.
Well Fed (3 upgrade points): Your Burrow lasts longer if you are not moving or you are moving at a really slow pace. This can be good if you want to wait for enemies to approach or you want to sneak away from enemies. It is useful if you waiting for something specific to happen, such as waiting for your other abilities to recharge. I find this upgrade alright, it does not seem as useful as the other Burrow upgrades, but there are a handful of situations where it could be useful.
Mastication (4 upgrade points): It takes much less time to digest an enemy, which means you are not vulnerable for as long after digesting an enemy. It makes it much easier to survive after eating an enemy, compared to normally where a Chomper would get vanquished after eating an enemy, but with this upgrade you have a higher chance of escaping and then going in for another vanquish after. I see this upgrade as greatly useful, being able to survive more easily after eating an enemy is not something you always every day, unless eating a lone enemy of course.
There is also an upgrade that indirectly boosts Burrow called Symbiosis. It costs 2 points and creates a Spikeweed at your current location when you eat an enemy after coming out of Burrow, it does not benefit the Burrow itself, but thought it should be mentioned here.
Conclusion
Burrow can really be a useful upgrade, especially on a character that is mostly limited to close range. It serves as a good way to approach enemies or even to get away from specific situations if needed. It is additionally a great way to get around in a stealthy fashion. In BFN, this is the only way to eat your enemies, although in the GW series, there are other ways you can eat your enemies but this is the most efficient way to do so. I find this ability really great, it helps the Chomper survive and fulfill its job very well.