doctorbadwolf
Heretic of The Seventh Circle
Well, not quite. THey're right that casting a spell within 5ft of a character with Mage Slayer procs an Opportunity Attack, they're just houseruling the OA to interrupt rather than follow the resolution of the spell.That's not a rule in 5e. What the heck?! Mage Slayer only affects Concentration Check.
It's a perfectly reasonable houserule, as is further forcing the caster to make a check to not lose the spell when that OA is taken and hits, but it is a houserule (or a misunderstanding of the rules).