Not much to say here- the Cautery sword as-is is a joke. Nightblade extends to 5* and does better damage against Slimes than the Cautery Sword when both are 3*. Also, Cautery Sword deals Normal - Nightblade is better than it against Gremlins.
So, let's change it.
Proposal: The Cautery Sword line extends to 5* and is changed to a low-damage healing weapon.
The 3* Cautery Sword should do equal damage to a typical 2* Normal-damage weapon, ie. Calibur. It has a usual attack pattern - three swings, normal speed. Each star-level upwards will do less damage than the equivalent Calibur-line sword.
The charge attack is limited-use: you can only use the charge when you have done enough damage to enemies. The amount of damage you have done is shown as a line on the charge meter. When the line reaches the maximum, you may use the charge. (Since it is limited like this, you can cancel a charge if it's ready by pressing 'Shield'.)
The charge will do different things for each weapon:
3* Cautery Sword: The charge will produce a small area in front of the user which lasts for one second, in the shape of a green heart (with the point back towards the user). The user is not in the heart and will be immobile from the charge long enough that they cannot move into the heart. Any Knights inside the area will immediately be cured of all Status Effects.
4* ['Revitalizer' - I need a better name for this]: The charge produces a slightly larger area in front of the user which lasts for one second, in the shape of a white heart. Charge mechanics as before. Any Knights inside the heart will instantly be healed.
Following Autofire's helpful post, this will now have different healing levels in different tiers:
-In Tier 1, it will instantly heal 1 pip of health.
-In Tier 2, it will instantly heal 2 pips of health.
-In Tier 3, since the damage of monsters is considerably higher, it will instantly heal 5 pips of health.
5* Scalpelissimus: The charge produces a large area in front of the user which lasts for several seconds, in the shape of a red heart. The user starts inside the heart, but is immobile for the same length of time. Since this is the 5*, there are special benefits: the large heart will heal all Knights inside at the same rate as a T1 healing pad while they are in it and will grant a temporary damage reduction while they are in the heart.
Again, after Autofire's post, I tweaked it to have different healing levels in different tiers:
-In Tier 1, the heart will last for 4 seconds and will heal a maximum of 2 pips of health.
-In Tier 2, the heart will last for 6 seconds and will heal a maximum of 3 pips of health.
-In Tier 3, the heart will last for 12 seconds and will heal a maximum of 6 pips of health.
Post feedback below, please!
-Raisin
Edits:
26/10/13: Scaled the healing levels of each weapon to the tier which they are in (tyvm, Autofire).
Hmm...
How does it scale is lower tiers? The 4* one would be broken in T1. (Okay, who cares about that? xD)
Otherwise, it doesn't sound too bad.