You can finds lots of videos about this on youtube, for example by hellhades.

You will need a significant amount of shards. Something on the order of 5 sacreds, or equivalent amount of ancients. If you don't have this yet, you should just keep stockpiling. But note that even if you can't get the big fusion, sometimes the epics are really worth it, and you can snag one of them without spending any shards. 

I would go light on potions if you can't beat stage 20 yet. It is a huge energy investment, and you don't know what colors you'll need. They can be farmed during the fusion if you have gems saved up.

Other than that, you'll need food and gems, but also a lot of silver. 2-3 artifact events is something like 40-60M silver. You'll get some of that during the fusion, of course, but it won't be comfortable at all to go in broke.

And finally, the most important advice: if you can't go all the way, don't go in at all! A half done fusion is a huge waste, which will leave you too drained to do the next one. If your account is not quite there, just save up. A good fusion will come along sooner than you think.

cheers!

Shards you can open during summon rush fusion event. 

The epic Hoskarul could be obtained without any summoning event. But for legendary champs, is commen to have a summon rush (shards count, 500 points per sacred) and a champion chase (champions count, obtained by any way).

For champion chase tournaments, it's good to save up the fragment champs and summon them during the tournament. I did not summon Hoskarul yet, for example.

I addition to that, you could level up champs needed for the Relickeeper fusion. 250 tournament points per epic.

Oh. So if there's a legendary fusion event, it's pretty much just for established players then? :(

At least a few months in, yeah.

Found an article on HH detailing the resources required:

https://hellhades.com/be-prepared-for-the-next-fusion-event/

[quote]

• 40 Lesser Void, 36 Greater Void, 6 Superior Void
• 40 Lesser Force, 36 Greater Force, 6 Superior Force
• 40 Lesser Magic, 36 Greater Magic, 6 Superior Magic
• 40 Lesser Spirit, 36 Greater Spirit, 6 Superior Spirit
• 80 Lesser Arcane, 108 Greater Arcane, 12 Superior Arcane 

• 48x 3 Star Chickens
• 16x 4 star Chickens 

You should have a collection of unleveled artifacts because historically speaking, in recent fusions there have been 2 Artifact Enhancement events during the Fusion Period.

Please note, every Artifact Enhancement event should be expected to cost upwards of 10million silver, so make sure you’ve got a stockpile ready to go, you’ll need it. You can also pre-level artifacts to 11 or 15 to bank some fast, easy points as soon as the event arrives to save yourself both time and valuable silver during the event. 

[/quote]

Just spent 500 gems on the gem mine as per HH's recommendation, so that's out as a source for energy refreshes. 

I managed to complete the Hoskarul event, only just, but looks as though I would completely struggle to complete a fusion event.

Which would be a shame, because it seems a big difference between Summoners War and Raid is that SW rewards players for taking part, ie, the number of times a dungeon was farmed or for the amount of energy used - while Raid appears to only reward players for the points earned while doing so. 

I'm not trying to make a big complaint of that - I know from SW how important it is to keep experienced players engaged with challenges - it just kind of niggles to join something new only to feel automatcaily excluded from the Big Christmas Party. :)

Still, I'm expecting to be able to open a couple of Sacred Shards in the double event just before Christmas Day - I'm not expecting to get a legendary, but a couple of new epics should still be exciting for me. Just hope it doesn't feel overshadowed by anything I might be missing out from. :)

In the meantime, rather than push to store up resources for fusion, I figure better to just focus on trying to build up what champions I do have into decent dungeon teams.

Well, sod it, I'm going for it. If I can manage to complete the Hoskarul fragment event within 2 weeks of joining this game, surely I can complete a fusion as well so long as I prepare in advance?

Therefore yesterday I started building up my food - I figure I need to make 100 x 3*, then turn 52 of those into 4*. Helps that I completed the campaign on Brutal yesterday so can farm 12-3 to max efficiency. 

In the meantime I'm farming the essence dungeons, and while I can only farm the Spirit dungeon to level 8 (I have no heal blockers) I've managed to get half the spirit potions I need already using auto-battle, which is definitely good. :)

Also helps that I've now unlocked the Advanced Quests which offers another source of energy refill plus other essential items - though I may not be able to complete it everyday.

Maybe I just felt over-whelmed originally watching the HH video on this, but now I'm going to try for it. :) I just hope I get to spend my Christmas money on something fun like shards and runes, rather than missing essential for the fusion such as potions!

Btw, is the fusion event likely to use the new monsters released last week, or would it be another new set of monsters specifically for the event?

Not sure anyone mentioned brews - these help save a pile of energy and time when levelling up champs.  And don't forget to level up your 3s and 4s partially even when using them to rank up as that gains a pile of champ training points.

Good luck!

The fusion will be using new champions that will be released around the time the fusion starts.

If you are willing to buy shards and/or gems you can likely complete any fusion.  On my first fusion I had to buy a few shards.  I got a great champ and it was worth it.  Pay attention to how the forum rates the champ.  The forum will tell you if its a cant miss champ.  

I am still learning that I cant complete every fusion event for free.  Its hard for me to let some get past me but I have learned its best to save resources for the great champs.  Its just like playing poker.  You have to know when to go all in.  

If you cant do a fusion its not the end of the world.  They come along every month and several each year are Godlike.  

Since, its the Christmas fusion, dont feel bad about spending some money on the game.  I try to be F2P but I will spend modestly for specific goals.  A Godlike champ is worth pulling out the credit card.