Ninth uitvibic. Ideas from comments.
1. Goblin invasion should have somesort of leader, like a Goblin warlord. He would use huge mace as weapon and drop it when he dies. Or a arcmage, who would shoot Chaos balls, Fireballs, AND waterspheres, dropping random spell on death.
2.Swamp biome was mentioned on some comment, but how about corrpution having corrupt water, that would be very sticky, and when under corrupt water, you could not hold your breath for as long time as in normal water.
3. Jungle boss. Somekind of giantic plant, with many man-eaters as heads that shoots out stingers. Might be able to walk by uprooting. Or by attaching one of its heads to ground, then dragging itself onwards to attached head. Maby heals itself by consuming water from water pools, or from mud, turning it into dirt. Damaged, or unable to root in sand.
Post your ideas on comment section below.