Casting the same global spell at the same time

[Cainehill]

Yep. The only way it might have been in question would be if you both had cast the bare minimum of gems necessary (or otherwise both cast the exact same number of gems), in which case I'm not sure whether the attempt to dispel/overwrite the other would be 50%, or if it'd simply be the order that gave a 50/50 chance for which had the spell succeed.

Could be worse - it could have been a really expensive and valuable spell like Forge of the Ancients (80E minimum) or Arcane Nexus (150 Astral minimum). It happens - I was in a game where I as Man and someone else as Vanheim both cast Forge of the Ancients on the same turn. Because I put extra gems in, his went poof without him getting any benefit from it.

The moral, perhaps, is to _never_ put the bare minimum into any global spell. Even towards the beginning of the game, putting an extra 3 gems in means that someone else, who might try to override yours by putting a mere 1 extra gem into the casting, will have wasted hir gems. Even better, if you can manage to put an extra 10-30 in for an early cheap spell like Mother Oak, other people will quite likely be totally throwing away large quantities of gems while trying to dispel or overwrite yours. For some of the really big spells (Arcane Nexus or Forge), put everything in that you can afford; that, or with the Forge, make sure you're prepared to get a big profit even if you only have the spell up for 1 turn.