Heal is one of the four basic spells in Eamon, and also features in subsequent, related game systems such as SwordThrust and Knight Quest. The spell is a form of universal magic and, unless specifically disabled in an adventure, works everywhere.
Hokas Tokas teaches the Heal spell to adventurers in the Main Hall. In both Eamon and SwordThrust, the base price that Tokas charges to teach the spell is 13000 gold pieces, which is then adjusted based on both the adventurer's charisma and a random number.
The Heal spell is of significant benefit to adventurers since it provides a way to restore lost hardiness without requiring a healing item such as food or a potion. It also helps an adventurer keep his or her companions alive through difficult battles.
It also seems that the Heal spell is the most reliable out of the four, since even on occasions when Blast, Speed, and even Power fail to work, Heal often still remains. For example in Thror's Ring, the adventurer's Heal spell is modified by the Lady Galadriel to work only five times, while in Curse of Talon, the chances of casting the spell successfully gradually decrease until the spell is unusable.
When converting adventures to Eamon Deluxe, Frank Black on some occasions restored the Heal spell to its standard functionality after it had been modified by the adventure's author. This was particularly necessary in the adventures of Sam Ruby since he frequently limited the Heal spell in ways which reviewers found frustrating, such as in Forest of Fear where players cannot cast Heal on his or her companions.
In Eamon Pro, the "second level" version of the Heal spell is the Cure spell. The spell is acquired by purchasing the Heal spell as per usual and advancing to at least level two according to the Eamon Pro leveling system. Cure is capable of healing between 2 to 12 hits, with a 10% chance of being automatically cast a second time, effectively healing between 2 and 24 of the player's hit points.