The Four Talismans & Deucalion’s Downfall
The Tuatha De Danann, a mythical race in Celtic mythology, brought four talismans with them, each representing an element and direction; the Dagda’s Cauldron (Water; West), the Spear of Lugh (Fire; South), the Stone of Fal (Earth; North), and the Sword of Light (Air; East). 
We could have potentially seen these talismans:
- The Sword of Truth once belonged to King Nuada who had the epithet ‘of the Silver hand’ – Argent – I’ve theorised that Gerard’s sword is important, we’ve seen it mentioned at least twice this season; once where Principle Thomas pulled it out, and again in Visionary when Talia Hale mentioned Gerard’s broad-sword. It was said that those who the sword was used upon never recovered, and we’ve seen this for ourselves when the Omega was cut in half.
- The Spear of Lugh could be the spearhead we’ve seen multiple times on the tip of Deucalion’s cane. It has been focussed on quite a few times, so there must be more to the spearhead.
- Dagda’s Cauldron could be the lake since its element is water. The lake has always been a bit of a mystery.
- The Stone of Fal could be the hecatolite rock we saw in Chaos Rising. It feels like a waste if hecatolite wasn’t utilised more in the show.
The four talismans are similar to the suits on a tarot card deck – the wand (spear), cups (cauldron), swords and pentacles (stone since its element is also earth). 
There is a card in the deck called the Magician who has all four suits on a table before him, he is seen as the bridge between this world and the spirit world. The combined power of all four items is kind of like the deathly hallows.
The combination of all four talismans could be the downfall of Deucalion.
He might be killed or injured by his very own cane since the spear belonged to Lugh, who was the grandson of Balor . There are similarities to Balor and Decualion:
Balor was told a prophecy by the Druids that his grandson would be the one to kill him – Deucalion somehow came to know a prophecy that Scott had true alpha potential and now wants to either collect or taint him.
Balor locked his daughter in a crystal walled tower to prevent the prophecy from happening by keeping her away from all men – Decualion had Scott trapped in a crystal (hecatolite) walls; however, I think this was to trap Derek, not Scott. It could be that Derek somehow has a part to play in the trigger to Scott’s true alphaness (they are brothers now) and Deucalion wanted Derek out of the way so he could be what Derek would have been for Scott.
This would explain why Deucalion killed Ennis – he knew Kali would swear revenge.
Balor had a poisonous eye caused by fumes of a druid’s potion and anything his eye gazed upon died. This isn’t the exact case when it comes to Deucalion, but the fact that his glasses shattered after his demon wolf speech and the fact that Deucalion sees through his wolf, the importance of their eyes is hard to overlook.
It’s something that Balor does which triggers the chain of events to his downfall; he was greedy and tricked someone into getting what he wanted, and in revenge, they found Balor’s daughter and seduced her. As a result, Lugh was born – the grandson of Balor prophesied to kill him. Deucalion’s greed in collecting rare alphas, Deucalion pushing Scott to become a True Alpha is what creates the threat.
Lugh has the qualities of the god Lugus who is often seen as a triune god , comprising of the three deities involved in the three-fold death – Taranis, Esus and Toutatis . The Darach has been sacrificing humans to appeal to these three gods, perhaps to summon Lugus since the Darach believes they are the only one able to kill Deucalion.
Lugh is to Balor what Scott is to Deucalion. His downfall.