Prior to D&D5e, Forgotten Realms lore included various situational methods and circumstances that could change the way spells and spellcasting worked. For example, the 1e product Volos’ Guide to All Things Magical includes a lengthy section on the use of various materials as special spell components. Using, say, a star sapphire in the casting of globe of invulnerability would increase level of spells warded off by the globe (see VGtATM p. 51). On the other hand, consuming the herb spellbane detailed in the 2e product Volo’s Guide to Cormyr would entirely suppress spellcasting ability for a period of time (VGtC p. 110).
Faerûn has changed a lot across editions, however, and nowhere is that more true than in the way magic and spells work. Maybe those old methods of amplifying or weakening spells and spellcasting are still effective, or maybe they aren’t. Is there any lore either way in 5e-era publications, i.e., in the Realms as they are post-Second Sundering, circa 1489 DR? Are there any other, different but comparable methods available?
To be clear, I’m interested here in methods that are temporary, ephemeral, and external to the caster and/or target — not innate abilities, learned skills, divine gifts, etc. Magic items are fair game, as are special substances (magical or otherwise). Even locations with special properties that change the way spells function would fit the bill.