Uborg, Tomb of Yawgmoth lags everything

Was playing a game earlier and it progressed very far with many permanents on the battlefield and i finally found my urborg, played it and immediately the game started to lag really badly, it had been running very smoothly up until then. so a few turns go by and we are all complaining about the lag and i find a way to get rid of my urborg and the game starts running smoothly again. This is less of a bug and more of a card in need of optimization.