At first, Sil was going at a steady pace with the ice pillar moving the entire city. This was because moving it faster would require more MC points. Although Sil was a monster when compared to anyone else in terms of MC points back on Earth, this whole event had taken quite a lot out of him.
Moving an entire city, constantly freezing the water was no easy task, and on top of that he had his clones out fighting against deadly beasts at the same time. So moving the city slowly was so he would have just enough MC points to still deal with everything if they got out of hand.
If Wince had failed in defeating Yanny, if the Dalki was unable to take out the predators, and if Quinn was nowhere to be seen, then he would have to deal with everything.
Although the last statement seemed unlikely, from what Sil had heard it was quite common for Quinn to go unseen and suddenly disappear. But he didn't want to take any chances, until he had witnessed Dogthus grabbing his neck.