BARD class is awesome as well. It works well on teams that have Gaards Avatar and Euryali as it boost all stats on yellow cards by 1 per turn. SUNSPEAR class is great for red teams that use explosions. TITAN is said to be one of the strongest classes. SENTINEL class is gret for brown troops. PLAGUELORD is great for supressing loop teams and mythics. ORBWEAVER is often used by people to hide and seek their hero on teams where he is the key player. FROSTMAGE is another great suppression class.
Delves in Krystaria are new. 3 delves per day. If a card is destroyed in a delve it’s gone for the remainder unless it can be summoned. Yields ingots to max out weapon powers, shards to get treasure and delve specific troops, and sometimes souls, gold, or renown (pushes up point value of delve kingdoms). Delves can be upgraded through hoard to add permanent gold gains per day, increase skills, unlock delve pets, and increase level to handle higher level encounters in delves.
There are now 4 GUILD EVENTS: Raid, Invasions, Tower of Doom, and Guild Wars. They alternate week to week. RAID: kill boss over and over and accumulate boss damage points to unlock tier rewards as a guild. INVASIONS: destroy towers over and over again to accumulate total towers destroyed for tire rewards. TOWER OF DOOM: ascend floors of a tower to destroy dooms. Each floor has 5 rooms, 1 has an unlock scroll for the doom room, the others have scrolls that increase stats or give a benefit to climbing the tower. 25 floors is considered ascending the tower to the top, though you can keep going. GUILD WARS: the same as it was 2 years ago. PVP against other guilds; do your best to win 5 out of 5 matches each day for 6 days.
Individual events happen as well. BOUNTY: described to me once as, see how far you can get using some of the worst cards in the game. Unlock rewards based on points accumulated. The more Bounty specific cards you use in your lineup the more points you get per match. The rewards are worth it, try it out. Also the cards of course count toward kingdom’s.
PET RESCUE: rescue a pet to get bonuses to your race or kingdom teams. The higher the pet is ascended the more your perks increase.
FACTION ASSAULT: a limited time delve run with tier rewards.
CLASS TRIAL: Quickly boost the featured class for a limited time. Chance to outright purchase XP and Class weapons to cut grind. Tier rewards included.
DUNGEON: Complete 3 matches a day to get crafting resources for the SOUL FORGE.
SOUL FORGE: Use materials to craft troops up to mythic, orbs, ingots, trait stones and weapons.
GNOME VAULT: Use vault key to enter a battle in a vault for a high chance to get rewards.
ADVENTURES: Took place of daily tasks. Complete these for trait stones, glory, gold, souls, gems, and deeds.
KINGDOMS: Level goes up to 15 now using deeds. Deeds found in daily adventures and flash sales. Stars increase tribute, tribute chance, gold gain, and skills. Increase stars by completing listed requirements. CHALLENGES: Give tier rewards now.
HONOR: gain honor to earn extra benefits. Some people trade it.
I think that about covers it. Let me know if you have any questions. 
Welcome back to GOW!
regrets always comes after the start