The `npc_trainer` table
This table contains all the spells that each trainer can teach.
Description of the fields
Usually, this would be an entry of a creature referring to creature_template.entry. However, Biohazard included several trainer lists by refering to their id. For more information, see Reference_list.
The spell ID from Spell.dbc. If the ID is negative, it's pointing to a reference template.
The cost that the player needs to pay in order to learn the spell in copper (1 gold = 100 silver = 10000 cooper). If you get this information from a data site such as Wowhead, be sure to take into account that they usually post the discounted prices based on friendly to exalted with a given faction.
The required skill the player needs to have in order to be able to learn the spell. See ID in SkillLine.dbc.
The proficiency in the skill from reqskill that the player needs to meet in order to learn the spell.
The level the player needs to be in order to learn the spell.