Collection items with no MF recipe

I have a number of leftover trinkets from specialization collections, e.g. Riddle of the x, as well as the various karma-bought ones. These can be placed in the MF window, but cannot be placed together, nor be placed with anything else as far as I've seen. It seems unlikely that these would have a specific recipe since they can only be obtained once. Are they just enabled for the MF by mistake or is there some way you can actually forge them?

The trinkets are classified as exotic items for the sake of the 4x reroll, but it requires other exotic items of the Armor variety. As for karma items, Soulbound items generally are not accepted as mystic forge input to complete a recipe, but there are exceptions, such as the rare ring from one of the heart vendors (I think in Timberline Falls?).

4x exotic weapons or 4x exotic armor -> 1 exotic weapon or 1 exotic armor whose level is = to average of all inputs (more 80s, higher chances of 80)4x rare weapons or 4x rare armor -> 1 rare weapon or 1 rare armor, with a 20% chance of getting an exotic instead (unless output item is =< level 60)

A mystic forge stone or ectoplasmic stone counts as a Lv.80 item, but it is a wildcard.

For the trinkets you get from the spec collections in Path of Fire, I strongly recommend you use a black lion salvage kit (chance from black lion supply boxes on Day 4 of login rewards per week; 3 black lion statuettes a piece) on those you won't use to pry the sunset jewel. You can then exchange the sunset jewel in one of the general Amnoon vendors for a Black Diamond. That way, you will have a means to make anything Viper's related if you so choose, or repurpose it to mournstone or brandspark jewel.

With the change to Rune salvage, Jewels now have a 100% chance of recovery (since they can't turn into lucent motes). However, I do believe those items have a chance at Ectos, which BL kits help improve. But with BL kits becoming less frequent from the normal reward stream, I've found Master/Mystic being more cost effective, despite the lower drop rate on salvage. Theres also a thing where some high value sigils and runes go for more then items that contain them, making it worth salvaging for a side chance at ectos.