Evolution items come from crafting or from the Travelling Merchant. Some later items are raid-shop or event-shop only. The evolution catalog says it was still waiting for a revamp, so a Gem price below is the catalog price, not a receipt from a current lobby.
Before you buy
Match the item to the unit. Hat of the Conqueror is for Red Scar. Quake Fruit is for Whitehair. King's Idol is for Lulu. Demon Beads are for Martial Demon and are bought with 100 Blazing Shards at Red Scar's Raid Shop, not with Gems. Path Branch and Hidden Seal use Path Shards in that same raid shop. Soul Orb is a Hollow World purchase for Trickster and is separate from Thread of the Exile, which is the Gem-priced Trickster item.
The materials catalog on this site lists the rows that named a unit, an effect, and a price or a shard cost. Loose crafting counts on the source page did not name every ingredient, so they are not copied as recipes.
Trait cost and evolution
Evolving a Legendary into a Mythic transfers the trait. Rolling before that evolution costs 1 Star Remnant. Rolling after it costs 5. Units the trait page names for this saving are Fox Ninja (Beast Cloak), Usurper, Martial Demon, Gene, and Experiment X (Semi-Perfect).
Update 20 says some evolve requirements were reduced and that new evolve quests and special quests were added. Open the evolve screen on the unit you care about and read the current list. Do not buy a 7000 Gem merchant item, such as Forbidden Candy, Arsenal Briefcase, or Negation Box, until that screen asks for it.
What the item changes
Merchant examples, as catalogued:
- Red Scar, Hat of the Conqueror, 3000 Gems: +50% attack and Conqueror's Haki.
- Magma, Magma Fruit, 4500 Gems: +30% attack and +20% Volcano range.
- Prime Force, Shining Extract, 2000 Gems: +40% attack, a shorter Smash cooldown, and a knockback on Smash.
- Martial Demon, Demon Beads, 100 Blazing Shards: +200% attack, Disorder, and Compass Needle.
Those are the reasons to evolve, not a general power rating of the unit.
After the evolution
Check placement cap before you hunt Unique. A unit that wants three or four copies on the map loses the point of a trait that allows only one copy. Divine is the trait note's suggestion for high placement counts. Then return to Story or Infinite and confirm the new ability is the one you are upgrading with Yen.