RPGMemes

Pretty much how I DM.

Bosses have prep time. Glyph of warding can be cast on a page in a book, with trigger conditions specified by the caster. E.g. when a good-aligned creature with ≥8 int comes within 10ft of it.

Explosive runes are 5d8 damage (dex save for half) per glyph.

Nothing says it can't be cast on more than one page.

A 50 page book with a glyph on every page means 100 dex saves for 5d8 each. Evasion is nice but you'll fail a save eventually.

Your "friendly" neighborhood lich has had time to prepare dozens of these. That tempting library full of magical books might just be a TPK.

As a "consolation prize" at least the player gets to roll 100 d20s at once! Multiple times if they survive the first book.