What is this Ekko true damage? (PIC)

It could have been an Elixir of Sorcery, but don't take the death recap at face value; it's notoriously buggy. (I've been told that a Leona did 1800 true damage to me with Vi ult before. There was neither a Vi nor a Leona in the game.)

It was probably red buff. For some reason red buff doesn't show on death recap.