If we were to make it something like Precursor Golem, I think we should make it "When you cast an instant or sorcery, if it targets a creature you control with (mechanic name), all other creatures you control with (mechanic name) are targeted by copies of that spell." Also, what does everyone think of the mechanic being called Intertwine? I like the idea of Fateshare; but, Shared Fate sounds better, even if it is two words, so I would be cool with Shared Fate too.

The problem with all of your suggestions NorthernRaven, KalvinHobbez and NoviceMagician is that they are too wordy. Imagine seeing a reminder text that long on about 15 cards.

Intertwine is too close to entwine.

Destiny (Whenever you cast a spell that targets this creature, copy it for each creature it is destined with.)

It's not really that wordy. Most of the time you will have the effect be like "Whenever ~ enters the battlefield, destine it and another target creature you control" or maybe an activated ability to do it.

I love Soulbond and would love to see it return. It's got a lot of design space.

You forgot one key point to Fateshare KalvinHobbez, is that it applies to any player. Here are some alternate rulings. I prefer the last one, as it is short and concise and to the point. Just remember that what the ability really means will be pasted in here. I mean, just look at what Soulbond really means. That is a massively long text.

Fateshare (You may pair this creature with another unpaired creature when either enters the battlefield. Whenever a spell or ability would target a paired creature, its controller copies it for each other creature paired with it. Each of those copies targets the other creature(s) that are paired with that one. Whenever a paired creature would gain or lose an ability, each other creature paired with that one gains or loses that ability.)

Fateshare (You may pair this creature with another unpaired creature when either enters the battlefield. If you do, the paired creature gains fateshare. Whenever a spell or ability would target a creature with fateshare, its controller copies it for each other creature paired with it. Each of those copies targets the other creature. Whenever a creature with fateshare would gain or lose an ability, each other creature paired with that one gains or loses that ability.)

Fateshare (You may pair this creature with another unpaired creature when either enters the battlefield. As long as they are paired, changes in the power, toughness or abilities that apply to only one creature also applies to the paired creature.)

Er ... messed up a few words on the last version. Here's a redo.

Fateshare (You may pair this creature with another unpaired creature when either enters the battlefield. As long as they are paired, changes in power, toughness or abilities that would apply to only one creature also applies to the paired creature.)

Two out of the three descriptions you posted are longer than the description for my proposal. Also, your last version of Fateshare(the fixed one) is about the same size. Anywho, what about "You may pair this creature with another unpaired creature when either enters the battlefield. As long as they are paired, any spells or abilities that target one, are copied and target the other." I think that spells and abilities would make more sense than listing-changes in power, toughness, and abilities-because spells and abilities encompasses the same things, and more, it is also shorter than listing the changes.

This description is shorter than all the others by the way, so it'd offer more card room.

The two are fundamentally different NoviceMagician. With the way I have set up, say an opponent casts a Pyroclasm, will now it kills their creatures too. Say I have a Dictate of Heliod on the field. Will now it affects their creatures too. Say they have a voltron creature on the field, will now I gain all of that creatures benefits. I personally think that this is a lot more balanced than just saying you can copy a spell or ability, because that itself can cause serious problems with infinite combos.

First, Pyroclasm already kills their creatures to because it deals damage to all creatures; second, to deal with problems like Dictate of Heliod, we could change "target" to "affect."; third, infinite combos are inevitable in almost all sets, so we shouldn't build the mechanic to try and prevent them, as they will occur anyways.

Okay, let's take a step back and re-evaluate. Epochalyptik was right in that this was just going to cause problems, regardless of which path we take. Scrap fateshare and move on to create something different.

I actually want to suggest this, how about we just give solas only one mechanic? Instead, we give them auras that can give creatures soulbond/bonding with more than one creature. Soulbond is versatile enough that we can create two different styles to the abilities in pre and post-war.

I would caution you against that only because the idea of multiple bonds doesn't necessarily work as well with the idea of "pairs" and because it can make the field really messy once you have to keep track of multiple pairings between many creatures.

I believe that we should stick to the two mechanic idea. Lets just move away from Soulbond entirely for the second mechanic, better that we design something cool and new.

When the Solas was designed as a religious group I had the concept of Sunbound mechanics to help them in aggro. The fire elementals are powered by the sun and can not come out during the night much due to this. So I made a pseudo day-night cycle with the turns

Sunbound - As long as its your turn, this creature gets +2/+2.

Its simple, done in Magic before, and easy to utilize. I think it's even in colors with how Glory of Warfare is.

Another idea the Solas can maybe use in flavor to the way that they can be tribal and in numbers, the name can be changed.

Crown (Whenever this creature enters the battlefield put a power counter on target creature. Remove that counter when this creature leaves the battlefield.)

Creatures with power counters get first strike.

I could imagine a lot of air elementals with Crown buffing up a fire elemental in this case.

These are pretty cool. I could get behind this. It works well with red and white for minor control to get your guys going. And the lore! I kinda want to make my own tribe now lol.