If it is casting a spell of 4th level or higher, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, the creature's spell fails and has no effect.
For each spell of 4th level or higher on the target, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a successful check, the spell ends.
The Ascendant Dragon-Touched Focus has a feature which allows you to treat a spell as though it were cast at 9th level:
when you cast a spell of 1st level or higher while holding this focus, you can treat the spell as if it were cast using a 9th-level spell slot.
Now, the usual function of this seems clear enough - if I cast fireball and use this feature, I roll 14d6 damage instead of the usual 8d6. What is not clear is how other creatures treat the spell.
When attempting to counterspell or use dispel magic on a spell "upcast" through this focus, do you treat the target spell as though it were cast at 9th level, or at the level it was actually cast?
Note, I use scare quotes around "upcast" because the spell is cast using whatever spell slot you choose to use for it. A 1st-level spell "upcast" with this feature still consumes a 1st-level spell slot.