With ink-treader nephilim, if I cast two instants on the stack on Ink-treader, can I resolve the copies in any order or do they need to be cast in the order of the original spells?
When a spell is cast that targets on Ink-Treader Nephilim, its ability triggers. When the trigger resolves, copies of the spell are created for all other creatures the spell could target. Those copies go on the stack in the order of Ink-Treader Nephilim’s controller’s choice. The original spell which targets Ink-Treader Nephilim will always resolve last after all other copies of the spell.
If you want to cast another instant spell targeting Ink-Treader Nephilim at roughly the same time, you have a few options:
You could cast it in response to the trigger, in which case the new spell and its trigger go on the stack above the first spell and its trigger. This results in all the copies of the new spell resolving first, then the new spell itself, then the copies of the first spell, followed by the first spell itself.
You could allow Ink-Treader Nephilim’s trigger and some of the copies from the trigger to resolve first. If you do this, then the copies of the new spell and the new spell itself will resolve before any more copies of the original spell resolve.
There is no way to otherwise mix up the order in which the spells and their copies resolve. For example, there’s no way to have a copy of the second spell resolve, then a copy of the first spell, then a copy of the second spell, etc.
Confused? Yeah, it’s a bit confusing.
Let’s look at an example: You control Ink-Treader Nephilim and three Gremlin tokens. Your opponent controls three Wolf tokens. You cast Annihilate targeting Ink-Treader Nephilim. When the trigger resolves, you put all of the copies that target your opponent’s Wolves on the stack above the copies that target your Gremlins. You then allow the copies that target the Wolves to resolves one at a time, destroying the Wolves and drawing 3 cards. Once the last Wolf is destroyed, you cast Renegade’s Getaway targeting Ink-Treader Nephilim. Its trigger will resolve and create copies of the spell targeting your Gremlins. After all of the Renegade’s Getaways have resolved, you’ll have an indestructible Nephilim, three indestructible Gremlins, and four new Servos. Finally, the remaining copies of Annihilate will resolve. They won’t be able to destroy the Gremlins or Nephilim, but you’ll still draw a card for each of them.