Spider venom neurotoxin that blocks voltage-gated sodium channel Nav1.3/SCN3A in human (IC(50)=1 uM) and rat (IC(50)=1 uM). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Has no effect on human and rat Nav1.8/SCN10A. Has no effect on voltage-gated potassium channel human Kv11.1/KCNH2/ERG at 10 uM (Ref.1). Belongs to the neurotoxin 10 (Hwtx-1) family. 10 (haplotoxin-1) subfamily.