Countermagic Mastery

When you successfully counter a spell, you may spellburn 1 to make it backfire instead of just countering it.
Its caster may fry a spellburn spell to avoid this.

You have advantage on all Counterspell tests.
You have advantage on all Dispel tests.

You may take 20 on Counterspell tests outside of spell wars.
(This 20 can be brought into a spell war if someone tries to Counterspell your Counterspell.)
(Xanadar does not teach this to anyone.)

When an opponent in a spell war tries and fails to beat your Counterspell score, they cannot cast Counterspell anymore in that spell war.
They are ejected from the spell war.
Normally, an opponent in a spell war can keep casting Counterspell until they run out of magic. But against you, they only get to fail once.
(Rerolls can still turn a failure into a success)

When you successfully counter a spell other than Counterspell, its caster is spellbound until the end of its next turn.
You may make one free attempt to counter each spell that a creature that is spellbound by you casts, with a -10 penalty.
However, these free counters cannot trigger spellbind themselves, and spells countered in this way refund any resources spent to cast them.