---
title: Geis, the Terrible Spell
description: Description of the concept of the spell according to Celtic tradition.
author:
  name: Graciela Paula Caldeiro
  url: http://graciela-caldeiro.idoneos.com
canonical: https://mitologiacelta.idoneos.com/en/geis/
source: en/geis/index.md
---

_"Shame fall upon you if you do not take me with you tonight"_

[Gráinne, casting her geis upon Diarmaid](/en/309247/)

The **Geis** (which in the plural must be said "geasa") is a fearsome **magical enchantment**, used not only by the **druids**, the casters of satires (magical enchantments sung by a member of the priestly class) or the poets, but by any inhabitant of Ireland and probably of the entire Celtic world. Kings were subject to a great number of geasa, as were heroes; only the druids seemed to be exempt. The geis involves two instances: > 1. **A prohibition:** it may consist of not eating the flesh of a certain animal, not going to a certain place, or not receiving any guest after sunset.

> 1.  **The obligation:** it may consist of a command directed at someone, with the threat of being killed or, more gravely still, dishonoured.

The potion that [Tristan and Iseult](/en/296286/) supposedly drink by accident is the softened image of a geis, cast by Iseult to compel Tristan to love her. [Cú Chulainn](/en/310144/) dies because his enemies have induced him to transgress one of his geasa, which ultimately leads to the transgression of all the others. The geis thus acquires a notable importance in social and religious life, underscoring the significant role of oral enchantments in druidic rituals.