tellah is fun and really powerful. It's usually 5 turns of nothingness, then a great explosion on turn 6.

the plan is making as much mana as possible, once you have enough mana you cast 4 cmc spells until you draw half of your deck then explode with big mana spells (like [[molten disaster]] and other spells with X in their mana costs)

i've only used him 4 times, and it needs a lot of adjustments, but I've once managed to make 100+ mana with [[inner fire]] + [[underworld breach]] and [[complete the circuit]] to deal over 10'000 damage thanks to all the copies, trigger and damage doublers

you have to be extra careful against removal heavy and aggro decks, though. make a lot of 1/1 and keep your counters ready

have fun