It took me 13 battles with the Water Splinter to complete the daily quest at the Silver III level. Got my ass handed to me over and over again... so much so that I had to buy one neutral (rare) monster to get it done:
Prismatic Energy did the trick!
I've combined it to get it to the Level 3 but since I've bought a card extra I let it be for now. When I push for the level 4 splinters I'll combine it then.