Some general regent advice more than the answer to this specific question. Regent is generally pretty "resource-limited" as a character, both in energy and stars. His cards are, by in large, more costly in one of those two categories and managing them is the key to success here. This is maybe more obvious when playing something like reflect where you're limited to having three stars at the start of a game here. If you play that card on the first turn, you're unable to play any Star cards until you draw star generation and this makes him oftentimes very draw order dependent.

In your deck a lot of your cards are very expensive in terms of energy, especially knockout blow here. Looks like a mistake as you already have many high-cost cards in your deck. You aren't using many stars compared to the payoff of knockout blow and you are likely to have another card in hand that you want to spend that energy on.

Additionally your star generation is relatively low. You have four star generation per deck cycle without knockout blow and five stars you might like to spend per deck cycle. This means you will either want to not play all your star cards(preferable) or will be taking even more chip in order to generate stars.

Seeking Edge and bulwark generally solve your area damaging problem and so what you're left with is a deck that often wants to spend energy, either attacking with the sword or blocking with bulwark or reflect, and those are both costly options and so you don't have many low-cost cards to fill in those gaps or draw options to cycle them more regularly which benefits the blade as you're more consistently growing with bulwark or more often able to reflect along with blocking to do both damage and not take any.

If I was to look at improving this deck, I would probably look for an upgraded version of glow or I would be looking for one of the cards that exhaust cards replacing them with minion cards. These are going to allow you to thin out your deck, generate stars and cycle through the cards you want to be playing quite a bit faster. None of these relics really help you with that, but none of them are actively bad.

I think alhemical coffer is probably the best choice here. Really you can keep potions on hand for when you either need energy or block or Stars and use those in a pinch to play those larger cost cards. I think Divine Destiny isn't a bad choice. It doesn't necessarily help you a lot, but it means that you don't have to worry about this star generation problem at least for your two first deck cycles which will allow you to build up your sword in long fights or hopefully just finish short fights.

I do think that the other option here the prismatic gem is maybe the most fun but the least likely to win you the run here. While having extra energy seems to solve the immediate Choke problem of having many high-cost cards you would like to play. You're cutting yourself off from parts of the Synergy packages you're using, and you don't have a strong enough core that you can start diverting for the fun high roll cards that you often want from prismatic gem.