So originally I was trying to make a piece that split and then attacked by combining its two halves. I wanted it to be a melee (non-magic) unit, but couldn't think of a good theme, so eventually I gave in and just made a magic-themed unit:

I added the "slide to next space" after leap-attack because I thought it was interesting (you can perform the leap-attack if the space beyond the landing square is occupied, but can't go directly to that space or leap-attack if the landing square is occupied).

Edit: Just noticed that I didn't actually need "Unblockable" on the Move/Swap/Leap spaces (and in fact they just confuse things, I think) -- so imagine it without that bit of silliness.

Illusionist splits to MirrorMage (not available separately):

If one MirrorMage is killed, it obviously cannot combine back into Illusionist, so I gave it some extra utility with the temporary self-transformation ability.

It should be noted, however, that if one runs more than one Illusionist (of the same tier), it is possible to combine halves from the different Illusionists.