Before returning to Dion, you'll get to destroy any permanent on the battlefield, which can include lands if your opponent has a problematic utility land
The dragon should more than pay for itself right away if you can clear some creatures off the board before casting it
It's no wonder this card has gone to the moon with a super cool lucid artwork featuring our Terastalised Pokmon in the centre
That's pretty good, but you have to know how many times you are going to have less of those things than your opponents to really know
There are also other downsides, for example drawing two Gemstone Caverns as your only lands, finding it after you kept one lander with Otherworldly Gaze, etc
Their stronger attacks have high energy requirements, which make them a bit costly and time-consuming to set up but ultimately worth it