There are only seven weapons that can stun all enemies:
The Doomed weapons can only stun enemies of the same color as the weapon, however. Orc King’s Club says stun all, but it only refers to the initial enemy and the splash damage, so it can only stun three at max.
That means Krysta’s Scythe is the only weapon that can literally stun all enemies. Applying a status effect to all enemies is something usually reserved for very specific weapons or troops. For instance, there are only three weapons that can burn all enemies (Fiend Fire, which curses them first, and Fell Ward, which burns all OR diseases all, and Dragon Slayer, which has the trait Mass Flaming).
There are also weapons like Wild Hunter (and its Epic version Eagle Eye) which have the trait “Mass Marked” which Hunter’s Mark’s all enemies. Shooting Star Dispels all Enemies. Ice Aegis can freeze all enemies, but only if its target is a boss, and of course bosses can’t be frozen, so you technically can’t use it to freeze all enemies.
So now that we’ve established that inflicting negative effects on all enemies is rather rare, let’s look at the rest of the weapon. You stun all enemies, and then create 3 elemental stars. Elemental Stars are gems that are brown, blue, red, or green. They can be matched with any gems of those colors (so not purple or yellow).
Best case scenario – the 3 elemental stars are created next to gems they can match with, particularly 4-matches which could give you an extra turn. Worst case scenario, they’re made in a way that gives the enemy a match instead…
Immediately after casting:
This of course gave me the mana, but it also set up a 4-match of skulls for the enemy team:
I really wish they would have done something for Krysta’s Scythe like…
Stun all enemies, create 3 Elemental Stars, then explode 3 random Gems.