Teleport Trap requires line of sight to be cast somewhere, but not to where you're teleporting the creature.
The Necromancer didn't do a very good job of playing defense in either game. Starting with Libro + Death Ring is reasonable, but when your opponent plays 2 face down enchantments on their first turn, that should make you immediately suspicious. At minimum you should quick cast something to give you armor. Playing a chest piece during the quickcast phase of round 2 would significantly reduce the threat of attack spam. Alternatively, you could have deployed a Skeletal Minion and walled yourself in as your quickcast. In that case the walls should buy you enough time to summon at least one more creature, probably 2, and give you time to play some armor. Block, Reverse Attack, or Brace Yourself would have helped significantly, as would anything that gave you a defense you could use against ranged attacks.
Drain Soul is not a great card to use defensively, and it ate up a huge amount of mana. It's mostly good when you're in a damage race (or need to do 6 or less damage to win outright) and you both have armor and/or defenses, as it bypasses everything that weakens attacks. Neither of you had enough armor/aegis/defenses to justify using Drain Soul, and you didn't have enough damage output to keep up with the Beastmaster. You could have used Jet Streams and Hurl Boulder to try to match the damage output of the Johktari and still had the mana for a defensive card or 2.
The Necromancer really needs to devote a reasonable portion of their spellbook to defense because they are the most fragile mage in the game, and they excel at building a long term advantage. The issue is that if you don't have the tools to survive to the late game, your late game strength doesn't matter.
