3400g = 
+ 
+ 
+ 700g
300 HP 300 Mana 35 Armor 35 MR 20% CDR 50% base mana regen 50% base health regen
Unique passive - harmony: Increase base health regeneration by 100% if your health % is lower than your mana %. Increase base mana regeneration by 100% if your mana % is lower than your health %.
Unique passive - resolute: For each % of health you are missing, you take 0.25% less damage.
Technically the main point of Trinity Force is the Spellblade passive, which the Iceborn Gauntlet fills the role of well. However, a well-rounded tank item could be pretty good if balanced properly. 3400 gold is extremely steep for a tank; tanks stats are generally cheaper than damage stats because tanks generally have less gold than damage champions. Where 15 armor is worth 300 gold (1 armor = 20 gold), 10 AD is worth 350 gold (1 AD = 35 gold). 25 Magic Resistance = 450 gold (1 MR = 18 gold), where 20 AP is worth 435 gold (1 AP = 21.75 gold). Health is also 400 gold for 150 health, 1 health = 2.67 gold. 250 mana = 350 gold, so 1 mana = 1.4 gold. Finally, the health regen is worth 150 gold and the mana regen is worth 125 gold for 25%. Cooldown Reduction is also worth 26.6 gold per 1% CDR, gotten from subtracting the value of the health on Kindlegem from the total value, then dividing by 10 because it has 10% CDR.
So, to get the gold value of the stats, take the stats and plug in the formula. Knowing how much gold the stats are worth will then allow us to figure out how much we're paying for stats and how much we're paying for the passive effects, then we can also figure out how much we're paying for the Resolute passive by subtracting what the Harmony passive is worth, gotten by subtracting the value of the stats from the Chalice of Harmony's cost.
Skipping all the math, this comes out to have the stats on this item worth 3,483 gold in total. The Harmony passive is worth 200 gold, and the Resolute passive is then free. The numbers may not seem too high on this, but this item gives a lot of stats, maybe even a few too many. I would suggest cutting some of the extraneous value to get the item down to around 2500-2600 gold value from the stats, then make it 2800 gold. This makes it so that the item isn't too expensive for tanks to buy (the only "tank" items that go above 3000 gold at all currently offer some sort of damage stat to them as well, which significantly boosts their value) while also making it so that the only value you're getting free is the Resolute passive, which might be a bit too strong. Maybe limit it to taking 0.25% less damage from champions per 2% health missing? As it stands, the Resolute passive is the only reason that any tank would want to put in 3400 gold for this item because the stats are so generalized that they actually become useless for a tank to buy. I do say that there need to be more hybrid resistance items. However, to also offer every other tank stat in the game and the Resolute passive may be a bit too much.
Maybe have the passive be something entirely different, as well. Instead of damage reduction at lower health, maybe have it grant a large amount of health regeneration if your health falls below a threshold, based on your missing health.
