[RPG] How many sorcery points does twin spell use when copying a spell cast with a higher level slot


The sorcerer ability Twin Spell (PH 102) reads:

When you cast a spell that targets only one creature and doesn't have a range of self, you can spend a number of sorcery points equal to the spell's level to target a second creature in range with the same spell

How many sorcerer points do I have to spend when casting a low level spell with a higher level slot?

For example, I cast Ray of Sickness (a 1st level spell) using a 3rd level slot. Would I spend 1 sorcerer point or 3?

Best Answer

Casting a Spell at a Higher Level
When a spellcaster casts a spell using a slot that is of a higher level than the spell, the spell assumes the higher level for that casting. For instance, if Umara casts magic missile using one of her 2nd-level slots, that magic missile is 2nd level. Effectively, the spell expands to fill the slot it is put into. Some spells, such as magic missile and cure wounds, have more powerful effects when cast at a higher level, as detailed in a spell’s description.
—Player's D&D Basic Rules, page 78

Since the slot is 3rd level, the spell is 3rd level. Since the spell is 3rd level, 3 points are needed.

Note that, for many spells, a higher level slot does more damage, as well. Ray of sickness does two extra dice of damage as a 3rd level as opposed to 1st...