Maggot

A Maggot is a type of monster in the game. As their name suggests, they're blind, white insect maggots that lack any appendages. They crawl around the room slowly and aimlessly. They can also be found wandering about within libraries.

Charger
Chargers are a more advanced form of Maggot. They possess a smiling face of sorts and look quite harmless as they slowly crawl along without attempting to follow Isaac. If a Charger lines up with Isaac vertically or horizontally, however, they will immediately and quickly charge in a straight line towards him. Because they're usually encountered in groups, avoiding them quickly becomes a problem.

Drowned Charger
Drowned Chargers possess the same behavior of regular Chargers, but have 10% more health. They shoot four diagonal blood shots upon death. They can be spawned by Drowned Boom Flies upon death, as well as (at reduced health) by Drowned Hives.

Dank Charger
Added in Booster Pack #5, Dank Chargers behave similarly to regular Chargers, but have a much faster dash, bounce off of walls while dashing, and leave a trail of slowing Black Creep while dashing. When their charge ends, they have a short cooldown period before they start moving again.

Carrion Princess
A variation of a Charger that was added in The Binding of Isaac: Repentance.

They charge diagonally, similar to Carrion Queen. Much like the Carrion Queen, they can only be damaged by hitting their tail segments.

Small Leech
Small Leeches were introduced in The Binding of Isaac: Repentance. They are quite similar to Chargers and make the same sound effect, but they do not stop at obstacles and continuously chase Isaac. They are also very small in size and can swim over flooded gaps.

Primarily spawned by Prey and Lil Blub, and can be found in Buckets.

When in a room without water, Small Leeches make small, short hops towards Isaac.

Small Maggot
Small Maggots were introduced in The Binding of Isaac: Repentance. They are quite similar to regular Maggots but are variants that are very small in size. Shortly after spawning, they very slowly crawl towards Isaac. They are primarily spawned by Pustules, Level 2 Horfs, and Corpse's bosses.

Level 2 Charger
Level 2 Chargers were introduced in The Binding of Isaac: Repentance. They are exclusive to. Upon lining up with Isaac cardinally, Level 2 Chargers will initially charge cardinally towards him but will curve their trajectory towards Isaac's position if attempting to move out of the way. Level 2 Chargers move slightly slower than default Chargers.

Elleech
Elleeches were introduced in The Binding of Isaac: Repentance. They move aimlessly until Isaac lines up with them cardinally. They then will charge indefinitely at Isaac, not stopping at objects.

Trivia

 * Chargers are based on Ropes from the Legend of Zelda franchise, since both charge at the player when they are in their sight.
 * The behavior of the Dank Charger resembles that of the Charger from "The End is Nigh", another game made by Edmund McMillen.
 * Elleeches are the only Ascent enemy without "Tainted" in its name.
 * Their name instead is a portmanteau combining the words "Elite" and "Leech", still carrying its elevated status.
 * They also take the appearance and behavior of a Small Leech, so in a way, they could be called Tainted Small Leeches.