Mighty Protectors Siphon ability (pg. 66) is a great power, but one thing it does not work on is substances. Fortunately, it is fairly easy to add a home brew rule to fill the gap!
For Siphon Type Substance, the character mimics the characteristics of any solid substance touched. Include the Mimicry modifier when buying Siphon Substance.
To use Siphon Substance, look up the type of substance touched with the Equivalent Material shown on the Density Increase chart (MP p. 32). When the character has rolled enough points to attain the appropriate CPs of the material, he gains those CPs in Density Increase.
Absorbo has 2d12 in Siphon Substance (30), Mimicry (-10), for a total cost of (20) CPs. He wants to use his Siphon Substance ability on a steel wall. Looking at the Density Increase chart, we see that Steel is SR 11, adds 5/4/4/4 protection, adds 11 to Strength, multiplies weight by 11, and costs 27.5 CPs. Once he rolls 28 points or more he will have mimicked the properties of steel and gained 27.5 CPs in Density Increase, gaining protection, strength, and increasing his weight accordingly.