I keep dying to the Crystalith boss in the Moonlit Forest (around the Crystalith Hideout zone). Its ground slam sends out this ripple shockwave that keeps destroying me. Am I underleveled or am I missing something about the fight mechanics?
I've tried bringing food buffs but even with Grilled Fish I can't get it below half health before running out of healing items.
The Crystalith telegraphs the ground slam by raising both arms before slamming down. When you see that animation, dodge to the side to avoid the shockwave ripple. Watch for when it draws power from the central crystal and its abdomen starts glowing brightly; that's your double-damage window.
Also, stock up on Charged Blast Pellets for your Slingshot. Ranged damage lets you chip away safely between melee windows. Bring at least 50-60 pellets.
Bring Chicken Stewed with Mushrooms instead of Grilled Fish. It gives the Battle Spirit buff which boosts your attack power, and it stacks up to 5 times. You make it at the Gas Stove with 4 Fowl, 3 Mushroom, and 1 Salt.
Another thing people miss: make sure you're bringing enough healing food. Grilled Mushroom Skewers are great for the Moonlit Forest since you can gather Sunveil Shrooms, Moondew Shrooms, and Mirthshrooms while exploring the zones. Each skewer restores a solid chunk of HP. Also, don't leave the arena mid-fight or the boss resets to full health.