Ability: Recover 50% of missing health at start of turn.
Ability: Recover 25% health at start of turn.
I can see the effort involved in trying to keep these two creatures different, and that’s actually appreciated. They’re both Death creatures though, and while having identical or near-identical creatures in different classes might be nice, here it’s a little overkill. My suggestion is thus to leave the Cannoneer alone, as its ability is arguably the stronger when you need it, and instead to change the Mutant’s ability to something more like this:
Darkness Surrounding: Recover 10% of health at start of each turn for each of your Death creatures.
This allows you to divide these two creatures into seperate niches, with the Cannoneer for more general tanking / health recovery roles, and the Mutant into a Mono-death build.
Speaking of which, monoclass creatures are something I haven’t seen explored much yet in Siralim (though this may be a fault of not having unlocked all tiers yet). Race archetypes are common, in comparison, but creatures that specifically buff their class might be a good add. Concepts:
Veiled Healer - Cleric, Life Class
Has a 10% chance to remove all debuffs from a creature on its turn for each of your Life creatures.
Thaumaturgic Locus: Amaranth, Sorcery Class
Grants a +5 or 1% bonus to Spellpower (whichever is higher) for each of your Sorcery creatures. Always has Magic.
Primeval Hind: Hunter, Nature Class
Ability: Survival Instinct
Grants a 10% bonus to Speed/Luck for each of your Nature creatures. Immune to debuffs.
Howling Mirror: Doom Fortress, Chaos Class
Ability: Through A Mirror Darkly
Each enemy creature has a 5% chance to be afflicted with Scorn at the beginning of a battle for each of your Chaos creatures.
Runic Mummy: Mummy, Death Class
When one of your creatures dies, each of your other creatures gain 5% of its stats for each of your Death creatures.