From Ryzom Wiki
Blind is an affliction; a negative status effect that handicaps the target.
A creature under the effect of Blind will almost always fail in every action they try while they are blinded. They'll fail all their spell castings and constantly miss with their weapons. They also can't dodge or parry any physical attacks directed at them while blinded.
Blind as a spell
Players are able to inflict Blind on a target using the Blind spell from the Offensive Affliction Magic skill. This spell is first available at level 10 magic. Like with all affliction spells, a link must be maintained to keep the target blinded.
Players can increase their chances of resisting a Blind Affliction spell by wearing jewelry that raises their Desert resistance.
Enemies using Blind
Since homin mages are capable of casting Blind affliction spells, it may be used against you in PvP. It may also be cast against you in PvE by bandits or tribes guards, who do not need to maintain a link to keep you blinded. In particular, Blind is often used by the NPC healer guards at outpost battles.
Gingos and Kibans have special abilities that allow them to inflict Blind on their enemies respectively by kicking sand in their eyes and spitting ink in their eyes. Both these effects are not magical and thus Desert resistance will not help you resist them. Creatures that are immune to Blind spells similarly are not immune to these effects.