It's such a powerful effect in Standard ramp decks to have a creature both become stronger based on the number of lands in play and also ramp that number up when it enters, and that's not the only use case for Lumra
Thanks to essentially functioning as a temporary counterspell on a body, Aven Interruptor gives an incredible tempo advantage by both adding a body to the board and taking away something from the opponent
This is also why Burn is a very tricky matchup
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of Serah Farron or Crystallized Serah's first abilities)
4 Deep Clue Sea Get Investigating Deep Clue Sea, as the name might imply, is built around the investigate mechanic, creating Clue tokens while drawing extra cards