Appearance, stats, and behavior
They appear as pale, translucent creeper heads that can fly, though they tend to hover a few blocks above ground. With 8 hearts and a maximum of 3.5 hearts of damage per second, they're weak to well armed players but could be dangerous in groups. Players without a helmet take more damage, similar to anvils.
When a Hemo Stalker detects a player taking damage, they "smell" blood and become hostile. It flies quickly towards you and latches onto your head, and when it does it gains an armor rating equal to your own, punishing you for letting your guard down. You'll have to kill them to stop the damage, and multiple can latch onto you.
They have a small chance to drop a scroll, a new item allowing for some special enchantments. Basically, if you get a scroll you have to enchant it at an enchanting table, and that allows you to use it to give unique enchantments to your equipment.
can be placed on any weapon, enemies you deal damage to will glow for a time equal to damage taken by the entity.
unlike the Hemo Stalkers, you can see just fine with your eyes. This helmet enchantment enhances them, highlighting anything you can see with a colored glow. Purple for end, red for nether, green for overworld, white for player. This is NOT a glowing effect on them, it basically does the same thing but different colors and it can't work through walls.