Described herein, in part, are crystalline and salt forms of N-((1-(2-(tert-butylamino)-2-oxoethyl)piperidin-4-yl)methyl)-3-chloro-5-fluorobenzamide useful for preventing and/or treating a disease or condition relating to aberrant function of a T-type calcium channel, such as epilepsy and epilepsy syndromes (e.g., absence seizures, juvenile myoclonic epilepsy, or a genetic epilepsy), tremor (e.g., essential tremor), and psychiatric disorder (e.g., mood disorders (e.g., major depressive disorder)).