Even as-is in a two-color deck, it's a powerful tool to fetch a two-drop critter, sorcery or instant from your deck and cast it
Tellah has a ton of text on his card, with his most powerful effect allowing the player to sacrifice Tellah when casting a spell costing eight or more mana to deal that mana cost to each opponent
But the chasest of the chase are the serialized versions, which go for hundreds of dollars (even for cards with regular versions that cost a few bucks)
They just prevent damage, which, like gaining life, is rarely worth spending a card on
11 Baloo Ol' Iron Paws The Fight Like A Bear ability says your characters with 7 Strength or more can't be dealt damage
Even better, it is at instant speed, so you can cast it just before your turn starts and draw whatever answer you need on your turn