Slime boss soul: every 3 turns add a 0 cost bludgeon with exhaust and ethereal into your hand.

guardian soul: every time you gain block also gain 3 flame barrier.

hexaghost soul: whenever you draw a status or curse card, exhaust it and gain 1 temp hp.

bronze automaton soul: at the start of your turn add a seek and 0 cost hologram into your hand, they both have exhaust and ethereal.

collector soul: at the start of each turn deal 7 damage to a random enemy twice and gain 7 block.

the champ soul: at the start of combat remove all artefact from all enemies then apply 5 weak and 5 vulnerable to all enemies.

awakened one soul: at the start of combat gain 1 strength and 1 dexterity for every power in your deck.

Time eater soul: at the start of each turn apply 1 slow to all enemies.

Donu soul: at the start of each turn gain 3 strength, this effect triggers twice per turn if you have deca soul.

deca soul: at the start of each turn gain 3 plated armor, this effect triggers twice per turn if you have donu soul.

corroupt heart soul: upon pickup gain 99 max hp, 999 gold and increase your end of run score by 1000. this soul has a 100% drop chance if the ascension level is 20 or higher.

some (most) of those sound reeeally good but like in a funny way

here's some more soul relic idea's I got this time based on the base game characters and a few modded ones.

the method of obtaining a character soul could be either as a neow blessing (this would replace the boss swap option) or as a extra starting relic you obtain when entering neow's room.

ironclad soul: whenever a non minion enemy dies heal 6 hp and gain 1 max hp.

silent soul: after start of turn draw you can discard up to 2 cards to draw the same number of cards plus 1.

defect soul: at the start of combat gain 1 orb slot, gain 2 heatsinks, channel 1 plasma.

watcher soul: once per turn right click to activate, add a smite and safety to your hand, they both gain ethereal.

hermit soul: whenever you shuffle your draw pile deal damage to all enemies equal to the number of cards in the draw pile after it's shuffled.

packmaster soul: at the start of each turn you can choose 1 of 3 colorless cards to add to your hand, it costs 0 and has exhaust and ethereal.

thorton soul: whenever you draw or play a card gain 1 gold, whenever a non minion enemy dies or you shuffle your draw pile gain 10 gold.

The base game characters' souls is definitely an interesting idea

got another batch of soul relic suggestions to give.

pointy soul (obtained as part of the combat rewards during the masked bandits event): if the first card played during your turn is an attack, deal 7 damage to random enemy twice.

romeo soul (obtained as part of the combat rewards during the masked bandits event): if the first card played during your turn is a skill, draw 2 cards.

bear soul (obtained as part of the combat rewards during the masked bandits event): if the first card played during your turn is a power, gain 2 strength and 2 dexterity.

snecko soul (shop relic): at the start of combat gain confused, confused is now treated as a buff instead of a debuff.

shelled parasite soul (shop relic): at the start of combat gain 3 plated armour and 3 blur.

spheric guardian soul (shop relic): start each combat with 2 artifact and 10 block.

darkling soul (shop relic): upon pickup choose 1 card in your deck (excluding curses), at the start of combat add 2 copies of the chosen card into your hand.

Your base game character soul relics has been implemented