The term 'Algific' means 'slippery when frozen', and Algific Creepers are just that! They are strictly found in snow, but when dragged out of their wintery homes they are very slow. When walking on ice, snow blocks, ect, they will grow slightly (1.3x) and have very slippery movements, which is called their Frozen State. They will attack the player when attacked, and otherwise leave players alone. When in a Frozen State they will leave behind a trail of ice wherever they walk. They can hide in ice blocks and will pop out when it is mined in Frozen State and in hostile mode. They cannot explode.
Algific Creepers are found strictly in Tundra Biomes and The Descent and cannot be found anywhere else. There is only a 7% chance that an Algific Creeper will spawn in every 6 chunks.