Portal Knights

On the first island that you start the game on, there is a portal with 4 blue portal stones missing. You need to collect 2 blue portal stone shards to craft 1 blue portal stone. So you need 8 blue portal stone shards for this. They can be obtained by defeating enemies and also mining blocks. I had 10 by the time I finished all the tutorials.

Once you have 8 blue portal stone shards, go into your crafting menu and craft blue portal stones. Then place them in the portal slots to complete it and walk through for this trophy