cr:1.8.6d

If an effect would generate a multi-event, the player determines the order of the individual events after the parameters of the effect are determined.[1.9.2]

Example: Shadowrealm Horror has the text “As an additional cost to play this, banish 3 random cards in your graveyard.” When the effect is generated, 3 cards at random are selected as parameters for the effect, then the player may choose the order in which those cards are banished as part of the banish multi-event.

Example: Glyph Destruction Nodes has the text “Deal 3 arcane damage to up to X target heroes and/or allies.” The target parameters of the effect are declared when Glyph Destruction Nodes is put on the stack, but the order in which those targets are dealt damage is determined when the effect is generated.