THE POPULOUS BIBLE
C.23 Magical Shield
Magical Sheild is a defensive or offensive spel which will protect your followers from direct spells from enemy Shamans and fireballs from firewarriors. The spell can only be used on followers - never your shaman. You receive Magical Shield from a Vault of Knowledge on level 14: "Attacked From All Sides". You can have a maximum of 4 shots of this spell at once.
This spell is extremly cost-effective and each shot can affect up to 6 of your tribe's units, lasting 2 minutes. Magic shielded units are immune to directly cast spells, except hypnotise (hypnotised units will lose the magical shield).
An indirectly cast swarm will affect magic shielded troops if it passes over them as it would non magic shielded troops, and will knock magic shielded troops out of balloons (Swarm always knocks units out of balloons and boats, in the latter case resulting in all the units drowning). Magic shielded warriors and preachers are immune to firewarrior blasts. Shamans surrounded by magic shielded followers are immune to a lightning cast directly on her, but not indirectly. Magical shielded units are immune to tornados.
Magical shield is not very common in Populous online, due to it's immense power and annoyingness.