This is step 5 of 5. You have a full Rare and one line you don't want.
The decision
- Orb of Annulment removes one random modifier and adds nothing. It is a rare, expensive currency, so use it wisely.
- Chaos Orb removes one random modifier and adds one new one. It is a swap, not a full reroll.
- Keep it costs nothing and risks nothing.
Both orbs pick the line to remove at random, so they can remove a line you wanted.
When to stop
If the item does the job your build needs, stop. Every further orb is a gamble on a line you can't undo.

