Tribulation

Start by finding and mining Veil Ore with an Iron Pickaxe (at least).
Not only do you need this for nearly everything in Tribulation, but it will also trigger certain mobs to start spawning in your world: Jarbringr and Vaendur. 

Collect Mage and Warrior spirits, as they too are crucial. Once you have enough, a choice presents itself: Will you become a Hunter or Mage?

• To become a Mage, use an Orb of Veil and quickly consume Mage Spirits by right-clicking them until you become a Mage.

• To become a Hunter, craft and right-click an Orb of the Hunt and choose your starting maximum stats.

From there, you can start tiering up to get stronger and craft a Veil toolset if you haven’t already. Craft the Blade Essence or Arcane Drop and fight the bosses. After defeating them several times, you can then craft full Veil Armor.

Continue to the Nether, which will reveal you to two new things: Naturally spawning spirits and corrupt spirits, in addition to the Priests of Huoyo: The Huodren. Fight these fire-breathing priests to obtain their essence, and use it to craft new tools. When you feel ready (after enchanting, attuning and preparing), you can build the portal to Huoyo from Blackstone and use the Banished Soul portal igniter on it. After defeating the Rebirthing Flame enough, you can craft Sacred Armor. 

With more preparation, you can continue to strengthen yourself until you feel ready. Then, use the craftable Night Key to traverse to Astralis, in which the Freigh are sprawled across the land. Kill them until The Night Guardian spawns. After defeating him multiple times, you can craft the strongest armor available (for now): Astraean Armor. You can also craft Eclipse (the sword) and the Astraean Staff (if you’re a mage). Prepare yourself, because the last fight is not an easy one.

When ready, begin to brew Tempora - which is made by putting a clock with Veilbrew potions. Then proceed to a Tempus biome in the Overworld and kill Past Remnants to obtain Tempus Navigator Shells. Once enough are obtained (16), you must level a Cleric Villager to Master, and he will offer a trade of 16 shells and 64 clocks for the Tempus Navigator. Punch a female Past Remnant with the Navigator, and it will summon the Temporal Knight.

Good luck. 

Classes:

Mages are diverse, melee-ranged fighters with up to 4 spells available in their arsenal, in addition to a staff they carry which adds even more attacks. They can heal, grant buffs, fire explosions, summon and conjure. Mages can teleport using the Utility key, and can join Cults to gain extra unique abilities. They can also use Totems, which grant passive buffs at the cost of a passive mana drain. Mages progress by hitting ranged attacks with their staff and casting spells - this increases their max mana, which in turn, nears them to tiering up by the required XP.

Hunters are mostly melee-oriented fighters with up to 4 forms available for them to use. They are mostly focused on attacking, movement and countering, and their build can vary greatly in its own way. Hunters can use Blades, which grant passive buffs to attacks. They can also join a School, granting them an extra unique ability. Hunters require Attuners to tier up, and must be maxed out in every stat of theirs before advancing. This means starting with low stats makes your tier go up faster, since you have a smaller amount to level each stat.

Forms/Spells:

To use forms/spells, simply press one of the four keybind (Z, X, C, V, by default). Equipping Forms/Spells is through their unique menu, accessed by long pressing the Utility key.

Attunement:

Attuning is a feature in Tribulation exclusive to specific tools. To attune, you first need to craft a Rune Forge and a slate. Now apply the slate to an attunable weapon, and your weapon will have attunement slots, varying on the slate you used. Now get a gem of your choice by first crafting a Blank Gem, then using a Smithing Table with various boss items to get the gem you want.

If you want to tier up your gems, you can do so using the Artificing Station and boss items that you already are familiar with. Gems can reach up to Tier 5, giving you +5 points in that stat. Since you can have up to 4 slots with the best slate, that means you can have up to +20 points in a single stat. The stats, however, are yours to vary as you please.

Utility:

The Utility key is one of the five keybinds in Tribulation. By default, it is R. The Utility key is used to access the stat menu for Hunters/Mages (long press Utility while sneaking), used to open the Spell/Form equipping menu (long press Utility, no sneaking), activating Cult/School abilities (short press Utility while sneaking) or activating movement (short press Utility) - for Hunters, that means switching between walking speed and Hunter speed; for Mages, it means teleporting.

Bugs, issues, suggestions, feedback, collaboration and all similar things are to be discussed in the official discord, or if necessary, the comments.

Tribulation may be used in your modpack, so long as proper credit is given.  

This mod was made using MCreator.

Some potion effect textures contributed by CerebralSwirl.