Things you can do with maggots...
1. From ELH: Creature: Wormkin. Lich with maggot body instead of mummy body. No more need be said.
2. From Dragon: Spell: Wall o' Maggots. Easier to punch through than Wall of Iron, but ewwwwww. Memo to Self: Look up disease rules for gutsy characters.
3. Creature: Giant Carnivorous Maggot. About the size of your finger, necrotic poison (rots flesh), tries to burrow inside and nest, then lay eggs.
4. Creature: Parachuting maggots. Silk streamer used to fly in a manner similar to some spiders. Can smell rotting meat a mile away and land to breed in it.
5. Spell: Rain of Maggots. Like meteor swarm, but keep your mouth covered.
6. Item: Maggot Cloak. A special, flesh-gray cloak which allows you to squeeze through small openings, live on rotting meat, bite for 2d4 damage, and summon a maggoty swarm of vermin 1/day. Slight side effect: odor.
7. Spell: Maggot Mount. A horse sized maggot that can burrow at a move of 10 feet. As long as you duck and cling tight, it can carry you through the earth. 2d4 bite, STR 24.
8. Spell: Maggoty Finger of Death. Like Finger of Death, but creatures affected are consumed from within by maggots.
9. Spell: Maggotskin. Your skin is flesh-gray or grayish-pink, and slimy. You get +2 AC against bludgeoning weapons.
10. Spell: Maggoty Retching. Target begins vomitting up maggots, violently. Similar in effect to Tasha's Hideous Uncontrollable Laughter, only a lot grosser.