Before setting out to spread the Chiral network, Sam remembered that BTs had been "set off" by his blood on two separate occasions. On Sam's advice, Bridges began to look into the effects of his blood on BTs.
Hematic grenades come in packs of five, which are carried either as regular cargo or held inside a grenade pouch. Each grenade will use up some of Sam's blood when thrown. The grenades will draw blood from a blood bag if is equipped. Otherwise, they will draw blood directly from Sam's body.
- Hematic Grenade (Lv. 1): Draws 50ml of blood.
- Hematic Grenade (Lv. 2): Draws 50ml of blood, but can draw more, up to 100ml, by holding R2.
- Custom Hematic Grenade: Draws 75ml of blood.
The effect on BTs appears to be proportional to the amount of blood drawn into the grenade.
A single lv. 1 hematic grenade is enough to send a gazer back to the Beach. If Sam is grabbed by gazers, a single grenade can be thrown around him to break free of the BTs and escape.
A larger BT will require multiple grenades, for instance it might take six lv. 1 grenades, four custom grenades, or three fully-charged lv. 2 grenades, to finish off a large BT that needs to be hit by 300ml of Sam's blood.
When Sam has access to both custom grenades and lv. 2, their intended usage determines which grenades to carry. Custom grenades are better for spamming, always delivering 75ml of Sam's blood, but for careful and deliberate throwing, lv. 2 grenades are superior as they can deliver up to 100ml, or as little as 50ml for small BTs, optimizing the drain on Sam's blood supply.