Rolemaster RM/RM2/RMC
Cancel Essence/Channelling is for instant magic defense
Cancel Essence/Channelling seem pretty useless until you consider their most important factor; they are Instantaneous spells, this makes them class I spells and they require no preparation no matter what level you are.
Cancel Essence When a spell of the Essence realm is cast
against the caster (of cancel Essence) the attack spell must first
make a successful RR before the caster is forced to make a RR.
So this is a defensive spell to save the caster from being blasted; the first key combat stages in Rolemaster are:
- Spell Phase
All combatants who will cast or prepare spells during the round must specify any pertinent information (spell type, target area, etc)
- Spell Results Phase
All spells specified in the previous phase are resolved simultaneously unless an exception is indicated by the GM.
Here is an example combat where Wizard Bob faces his arch-rival Wizard Anti-Bob.
- Spell Phase
Anti-Bob: I shall blast Bob with a shock bolt
Bob: I shall cast Cancel Essence
- Spell Results Phase
Anti-Bob: I blast Bob! Hahaha!
Bob: My cancel essence spell spell is up! Make a RR to make your attack.
Anti-Bob: <rolls and fails the RR> Curse you Wizard Bob!
This is the standard Rolemaster turn sequence from RMSS and RMC; this is of course complicated by the many different variants available through the Rolemaster Companions, but essentially all Instantaneous spells are reactionary spells (Like Bladeturn for example) that are there to save you from an attack or situation.
Note: In my games I used the standard AD&D style turn sequence: roll for initiative and each acts in turn. I let casters cast Instantaneous spells out of turn (using their spell up for that round) if they wished to react to something, it worked very well.
Rolemaster Standard System
The spells can still be used for instant defence - if you're a good enough caster.
All the spells on the "Dispelling Ways" (p16 Of Essence, p83 Spell Law) are no longer instantaneous, which means most of the spell list is now of dubious usefulness unless you're high enough level or take a penalty to cast them with zero round of preparation. For a same level spell this is a -55 to cast (spell casting modifications table T-4.6, p. 47 "Rolemaster fantasy Roleplaying) which isn't that bad a penalty if you're a good caster, long as you don't fail!)
"Cancel Essence" in Spell Wall (p14 Of Essence p81 Spell Law) and "Cancel Channeling" in Spell Defense (p14 Of Channelling) are all the same, so this isn't a typo/misprint it's an intended system change.
I can't say why ICE made this change, what I can say is that the change makes the spells pretty useless/more dangerous at low level as you'll have to fast-cast them. So I agree, as is, the spell is pretty pointless - I'd revert the change and make them instantaneous.