Nicola Tesla is shuffled into the age 4 deck, then bought like any other advisor. It is recommended to include him only when you have played a couple of games with the expert deck.
Nicola Tesla was a larger than life genius who, amongst many other things, developed the alternating current standard for electricity that is used throughout the world today. Known for his prodigious ability to invent, he became very rich. However, he spent most of his money pursuing new inventions. In Nations this is reflected by his ability to provide a random increase in military strength if you provide the extra funding he needs. Use the die included in the game for the roll, this is the only use of the die outside of the solo game and is not recommended for eurogame purists.
For more information: http://boardgamegeek.com/boardgameexpansion/149245/nations-nicola-tesla-promo-card
Hagia Sophia is shuffled into the age 2 deck, then bought and built like any other wonder using architects and stone. It is recommended to include it only when you have played a couple of games with the expert deck.
The Hagia Sophia of today is actually the third iteration as it had to be rebuilt due to being burned down during riots twice. That is was subject to internal destruction combined with the later conquest by the Ottomans inspired us to make it possible to lose the wonder. This card is very much a high risk/high reward card and the 4 Victory Points can help you out immensely if you manage to keep it the whole game.
For more information: http://boardgamegeek.com/boardgameexpansion/149246/nations-hagia-sophia-promo-card