Wretched Broker

The Wretched Broker is an NPC in the House of Hades's lounge area who offers repeatable trades for a number of collectable resources from Zagreus. The broker also offers a limited deal following each run. Each limited deal may only be traded once, and allows trading Darkness in addition to other rewards.

Repeatable Trades
Repeatable trades only let you convert materials in the sequence Gemstones → Chthonic Keys → Nectar → Diamonds → Ambrosia → Titan Blood. They do not let you reverse this sequence or make trades involving darkness.

Analysis of Limited Time Offers
There are three types of limited time offers available at the broker: indirect trades that give a better rate of exchange compared to what you can get with repeatable trades, trades that let you reverse the conversion sequence in repeatable trades, and trades involving darkness.

Values from the Item and Offer Price columns are what appear in-game (eg. 1 Nectar for 10 Gemstones).

Indirect trades
These trades convert resources in the same direction as the repeatable sequence Gemstones → Chthonic Keys → Nectar → Diamonds → Ambrosia → Titan Blood, but skipping steps and at a better rate. The Repeatable Price column shows how much you would pay if you used Repeatable Trades to obtain an item instead of the Limited Time Offer. The Savings column shows the percentage savings that the Offer Price represents, compared with the Repeatable Price.

Reverse trades
These trades convert resources in the opposite direction as the repeatable sequence Gemstones → Chthonic Keys → Nectar → Diamonds → Ambrosia → Titan Blood. The "efficiency" of such a trade is how much of the original resource you can get back using repeatable trades. Though the 1 Titan Blood → 200 Gemstones trade has the worst efficiency compared to repeatable trades, it can actually be used with the 15 Chthonic Keys for 1 Titan Blood indirect trade to get back more than you started with: 1 Titan Blood → 200 Gemstones → 20 Chthonic Keys → 1 Titan Blood + 5 Chthonic Keys. You can also use the alternate sequence 1 Titan Blood → 200 Gemstones → 20 Nectar → 2 Ambrosia → 2 Titan Blood, but this involves 22 separate indirect trades and would take many runs to accomplish.

Darkness trades
The 3 other currencies (Nectar, Ambrosia, and Chthonic Keys) are converted to Gemstone equivalents via Repeatable Trades. For the first two rows you can think of this as letting you buy darkness with gemstones (indirectly using repeatable trades). For the last two rows, you can think of this as letting you use darkness instead of gemstones to buy items.

Extra: The Wretched Broker will smile at you if you look at the Employee of the Month.