Animal friendship
From Ardrana
By means of the animal friendship spell, the caster is able to show any animal of limited intelligence that he desires friendship. If the animal is affected, it stands quietly while the caster finishes the spell. Thereafter, it follows the caster about. The spell functions only if the caster actually wishes to be the animal's friend. If the caster has ulterior motives, the animal always senses them (for example, the caster intends to eat the animal, send it ahead to set off traps, etc.).
The caster can teach the befriended animal specific tricks or tasks. Typical tasks are those taught to a dog or similar pet (i.e., they cannot be complex). Training for each such trick must be done over a period of one week, and all must be done within three months of acquiring the creature. During the three-month period, the animal will not harm the caster, but if the creature is left alone for more than a week, it will revert to its natural state and act accordingly.
The more powerful the caster, the more animals he can attract -- or he can attract more powerful animals. Only unaligned animals can be attracted, befriended, and trained.
Note: This spell originally appeared in this form in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.