Create Bonfire + Repelling Blast

[Mr Adventurer]

Bonfire specifically states that the bonfire fills a 5' cube and that creatures must be in its space to take damage. Hypothesising about how hot a real 5' fire would be is off the mark.

To affect 4 creatures in a 2×2 arrangement, you place the bonfire presumably in the middle, where one quarter of it intersects with one quarter of each creatures' space.

I play and DM. I wouldn't expect this to work as a player. As a DM I assume you simply pick a square for it to affect. If a player agitated otherwise, I'd give advantage on the save.

I'll be honest though: I actually just use 3.5 edition spell areas for grid play.

Edit:

The abstraction is exactly why a five foot cube placed on the grid corner makes sense, though. The question arises where the targets are in their own spaces. But they do get a dexterity save to negate damage, which only makes proper sense if there’s space to dodge to. If it’s in their square rather than on its corner, there’d be no such place. So the Dex save represents them scrambling to the 3/4 of their square it’s not in.

You get a save no matter how much of your space is covered by an area effect.