Valedictorian

You are a master of the arcane arts, and graduated from your spellcasting academy at the top of your class.  You gain the following benefits:

• You have proficiency in Arcana if you didn't already have it before.
• You can learn new spells at half of the time usually required to write them down.
• Once per encounter, you can use a bonus action to choose a target.  If the chosen target has casted a spell in the last minute, you may roll an Intelligence (Arcana) check to try and understand the targets magical strength.  On success (under DM's discretion), you learn what the target's spellcasting ability is, what their spell attack modifier is, and what their spell save DC is.  You gain advantage on all saving throws done to contest a magical ability or spell from that target for 18 seconds.