Spend only mana produced by basic lands to cast this spell.
"An ancient, powerful force has overtaken the valley. I sympathize for its former inhabitants, but I rejoice for the land itself." —Olanti, Muraganda druid
2021-03-19
An effect that allows you to spend mana as though it were mana of any type to cast Imperiosaur won't allow you to spend mana from a source other than a basic land to cast it.
2021-03-19
If a basic land gains a mana ability, mana produced with that ability can be spent to cast Imperiosaur.
2021-03-19
If a triggered mana ability produces mana when a basic land is tapped for mana, that additional mana is produced by the source of the triggered mana ability, not by that basic land.