Hello there. Thanks for the comment.
As for the power: yeah, the only way to damage it is with K, which is the attack button. We had more power ups already developed, but because of time, we couldn't upload them (and also it was an oversight, we intended for this demo to have all power ups unlocked from the start). The only way now to have a power up is to talk to the shaman at the start of the game (with E).
The yellow exclamation was just for demo purposes (for testing the interaction system), there will be a checkpoint in its place (a bonfire). We just left in there because.... we didn't have any other better alternative.
Still, thanks for the feedback, as the previous comment has mentioned, we couldn't complete the game for personal setbacks, but we intend to complete it and make it more playable.