4Clash Royale card guide
Tesla is a defensive building that hides underground when it isn't attacking. While hidden it can't be hit by spells, and it hits both air and ground.
Place Tesla in the middle of the lane to pull Hog Rider, Balloon and other building-targeting cards. Since it hits air and ground, it's very versatile. X-Bow decks use it to protect the X-Bow.
Cards that deal with it efficiently:

This card has an evolution. The evolution is active in your deck’s 1st (Evolution) or 3rd (Wild) slot. The Evolution slot unlocks at Arena 3, the Wild slot at Arena 10.
ElixirDeck automatically takes your unlocked evolutions and heroes into account: build your decks.