Both T7 affixes need to be in the prefix category because those are the ones intended to Last Epoch gold transfer. Suffixes are considered optional bonuses.

The starting item contains:

Empty prefix

T1 Crit Multi

T7 Elemental Res

Cold Res

Not ideal, but usable.

Step 1: Fixing the Prefixes

The first task is establishing the correct affixes. Spell Crit must be added to fill the second prefix slot. Both prefixes start at tier 1, which is acceptable because upgrades will follow.

Glyphs of Hope should be used during the entire process to preserve Forging Potential. Once potential reaches zero, the item is finished.

Spell Crit is added with only two potential losses-an excellent start.

Step 2: Shifting Tiers Into the Correct Slots

Next comes the critical step: using Runes of Havoc. Havoc shuffles the tiers among all affixes. The goal is to pull the T7 Elemental Resistance off the suffix slot and into a prefix position, while nudging the T1 prefixes upward.

This typically takes multiple attempts and often ruins items. But this time, the shuffle lands perfectly:

The T7 moves onto Crit Multi

Spell Crit rises to T4

A near-ideal setup for a high-value slam.

The item now contains:

T7 Crit Multi

T5 Spell Crit

T7 Elemental Res

Cold Res

Now it's time to plan upgrades and risks.

Step 3: Choosing What to Upgrade

With a 2-LP unique, only two affixes will transfer. That means attention should be focused on:

T7 Crit Multi (guaranteed)

T5 Spell Crit (desired)

Upgrading the resistances isn't necessary. Damage-focused prefixes are the priority.

Crit Multi is guaranteed to transfer during a Tier 2+ slam because a guaranteed affix may be chosen. Spell Crit has a 1-in-3 chance.

Since the Crit Multi roll is mid-range and Forging Potential is low, a Rune of Refinement can be attempted after upgrading Spell Crit-if potential allows.

Spell Crit is raised to T5 without losing excessive potential. Good outcome.

A Refinement is attempted on Crit Multi, resulting in a roll to 55-solid. With remaining potential, Elemental Resistance is upgraded for free.

Next step: duplication.

Step 4: Duplicating the Item (Rune of Creation)

With potential nearly exhausted, a Rune of Creation is used to duplicate the item. This produces two identical catalysts, each ready for slamming. Two attempts instead of one-an enormous advantage.

Step 5: Performing the Slam in the Temporal Sanctum

To create a Legendary, the following are required:

A unique with Legendary Potential

A matching exalted item

A Temporal Sanctum key

Enter the dungeon through the key and run Tier 2 or higher. Tier 2+ allows the guaranteed-affix mechanic needed for controlled slams.

The unique item in question requires level 36, qualifying it for Tier 2, though Tier 4 is often chosen for fun or familiarity. After defeating Julra and realm-swapping to cheap Last Epoch gold avoid mechanics, the Eternity Cache becomes accessible.