When this spell is cast, a hypnotic pattern is set up that causes one or more snakes to cease all activity except a semierect, swaying movement. If the snakes are charmed while in a torpor, the duration of the spell is 1d4+2 turns; if the snakes are not torpid, but are not aroused and angry, the charm lasts 1d3 turns; if the snakes are angry or attacking, the spell lasts 1d4+4 rounds. The priest casting the spell can charm snakes whose total hit points are less than or equal to those of the priest. On the average, a 1st-level priest could charm snakes with a total of 4 or 5 hit points; a 2nd-level priest could charm 9 hit points, etc. The hit points can be those of a single snake or those of several of the reptiles, but the total hit points cannot exceed those of the priest casting the spell. A 23-hit point caster charming a dozen 2-hit point snakes would charm 11 of them. This spell is also effective against any ophidian or ophidianoid monster, such as naga, couatl, etc., subject to magic resistance, hit points, and so forth.
Variations of this spell may exist, allowing other creatures significant to a particular mythos to be affected. Your DM will inform you if such spells exist.
Notes: Common for clerics and druids (PHB).