Critters are basic encounters in caves and dungeons, but the choice is very limited in 15mm scale. You can sculpt them yourself with green stuff or Fimo, make a mold, and cast hundreds of those. The first picture depict a kind of Staphylinus (in blue) and centipedes
The purple worm is made with Fimo paste. It’s a single piece, no mold made. A chemical reaction occured after varnishing the model, and the worm became tacky. Normal for a real worm, but annoying for a miniature.
Finnaly some Jelly, made with Fimo.